Question login not possible

But now, another problem occurs. The user has no permission to start a new topic. The following message is displayed:403 Forbidden : Entweder fehlen die Berechtigungen, um ein neues Thema zu starten, oder es wurde keine Kategorie der obersten Ebene erstellt/veröffentlicht! Die Seite kann nicht angezeigt werden, weil:

1. ein veraltetes Lesezeichen aufgerufen wurde.
2. über eine Suchmaschine ein veralteter Index dieser Website aufgerufen wurde.
3. eine falsche Adresse aufgerufen wurde.
4. keine Zugriffsrechte für diese Seite vorhanden sind.
5. Die angefragte Quelle wurde nicht gefunden.
6. Während der Anfrage ist ein Fehler aufgetreten.

There are neither obsolete bookmarks, nor has the page been reached by a search engine.
So, how should the user permissions be set?

So, how should the user permissions be set?

No, this is another error. Have you created the hidden menu again? If not, then enable the debug mode in the Joomla configuration and set the error reporting on "Server" tab to maximum. Also enable the debug mode in the Kunena configuration ("General" tab).
Then try to respond to get a more accurate error message.

No, I did not create it again.
Now, once again, although bootstrap is deactivated, I cannot login with the forum button, so I used the system login as site module.
But, now in Debug mode with maximum error report, there is the same error message when trying to start a new topic.

here is the current kunena system report:

Database collation check: The collation of your table fields are correct
        

Joomla! SEF: Enabled | Joomla! SEF rewrite: Enabled | FTP layer: Disabled |
        

This message contains confidential information

htaccess: Exists | PHP environment: Max execution time: 50000 seconds | Max execution memory: -1 | Max file upload:  

Kunena menu details:

Warning: Spoiler!

ID	Name	Menutype	Link	Path	In trash
1104	Forum	kunenamenu	view=home&defaultmenu=1105	forum	No
1105	Index	kunenamenu	view=category&layout=list	forum/index	No
1106	Recent Topics	kunenamenu	view=topics&mode=replies	forum/recent	No
1107	Unread	kunenamenu	view=topics&layout=unread	forum/unread	No
1108	New Topic	kunenamenu	view=topic&layout=create	forum/newtopic	No
1109	No Replies	kunenamenu	view=topics&mode=noreplies	forum/noreplies	No
1110	My Topics	kunenamenu	view=topics&layout=user&mode=default	forum/mylatest	No
1111	Profile	kunenamenu	view=user	forum/profile	No
1112	Help	kunenamenu	view=misc	forum/help	No
1113	Search	kunenamenu	view=search	forum/search	No

Joomla default template details : shaper_helix3 | author: | version: 3.0.3 | creationdate: Jan 2016

Kunena default template details : Aurelia | author: Kunena Team | version: 6.0.9.1 | creationdate: 2023-02-22

Kunena template params:

Warning: Spoiler!

DefaultCategoryicon
profileIconset	default
DefaultIconset	default
editorIconset	default
bootstrap	0
borderless	1
tooltips	0
SubjectLengthMessage	80
fullactions	1
quick	0
displayMenu	1
displayDropdownMenu	1
displayDropdownContent	1
displayModule	1
displayBreadcrumb	1
displayAnnouncement	1
displayFooter	1
avatarPosition	left
formRecover	0
labels	0
whoisonlineName	default
avatarType	rounded
topicicontype	svg
fontawesome	1
socialshare	1
socialsharetag
socialtheme	flat
optional_username	0
writeaccess	1
localstorage	0
IconColor	inherit
IconColorNew	#48a348
editorType	ckeditor
Bold	1
Italic	1
Underline	1
Strike	1
Subscript	1
Superscript	1
RemoveFormat	1
BulletedList	1
NumberedList	1
Blockquote	1
JustifyLeft	1
JustifyCenter	1
JustifyRight	1
JustifyBlock	1
Link_Unlink	1
Image	1
Smiley	1
Confidential	1
Hidetext	1
Spoiler	1
Code	1
Ebay	1
Twitter	1
Instagram	1
Soundcloud	1
FontSize	1
TextColor	1
Maximize	1
Map	1
Video	1
editorButtons
nameskinckeditor
ckeditorcustomprefixconfigfile
avatarSizeX	40
avatarSizeY	90
avatarSizeXThumb	36
avatarSizeYThumb	36
avatarSizeXWelcome	72
avatarSizeYWelcome	72
avatarSizeXList	36
avatarSizeYList	36
avatarSizeXPost	144
avatarSizeYPost	144
avatarSizeXProfile	200
avatarSizeYProfile	200
templatebyText
templatebyName
templatebyLink

Kunena version detailed: Kunena 6.0.9.1 | 2023-02-22 [ Git Repository ]
        | Kunena detailed configuration:

Warning: Spoiler!

Kunena config settings:
boardOffline	0
enableRss	1
threadsPerPage	6
messagesPerPage	10
messagesPerPageSearch	15
showHistory	1
historyLimit	6
showNew	1
disableEmoticons	0
template	aurelia
showAnnouncement	1
avatarOnCategory	1
showChildCatIcon	1
rteWidth	450
rteHeight	300
enableForumJump	1
reportMsg	1
username	1
askEmail	0
showEmail	0
showUserStats	1
showKarma	1
userEdit	1
userEditTime	0
userEditTimeGrace	600
editMarkup	1
allowSubscriptions	1
subscriptionsChecked	1
allowFavorites	1
maxSig	300
regOnly	0
pubWrite	0
floodProtection	0
mailModerators	0
mailAdministrators	0
captcha	0
mailFull	1
allowAvatarUpload	1
allowAvatarGallery	1
avatarQuality	75
avatarSize	2048
imageHeight	800
imageWidth	800
imageSize	1024
fileTypes	txt,rtf,pdf,zip,,tgz,
fileSize	120
showRanking	0
rankImages	1
userlistRows	30
userlistOnline	1
userlistAvatar	1
userlistPosts	1
userlistKarma	1
userlistEmail	0
userlistJoinDate	1
userlistLastVisitDate	1
userlistUserHits	1
latestCategory	0
showStats	1
showWhoIsOnline	1
showGenStats	1
showPopUserStats	1
popUserCount	5
showPopSubjectStats	1
popSubjectCount	5
showSpoilerTag	1
showVideoTag	1
showEbayTag	1
trimLongUrls	1
trimLongUrlsFront	40
trimLongUrlsBack	20
autoEmbedYoutube	1
autoEmbedEbay	1
ebayLanguageCode	en-us
sessionTimeOut	1800
highlightCode	0
rssType	topic
rssTimeLimit	1 month
rssLimit	100
rssIncludedCategories
rssExcludedCategories
rssSpecification	rss2.0
rssAllowHtml	1
rssAuthorFormat	name
rssAuthorInTitle	1
rssWordCount	0
rssOldTitles	1
rssCache	900
defaultPage	recent
defaultSort	desc
sef	1
showImgForGuest	1
showFileForGuest	1
pollNbOptions	4
pollAllowVoteOne	1
pollEnabled	1
popPollsCount	5
showPopPollStats	1
pollTimeBtVotes	00:15:00
pollNbVotesByUser	100
pollResultsUserslist	1
allowUserEditPoll	0
maxPersonalText	50
orderingSystem	mesid
postDateFormat	ago
postDateFormatHover	datetime
hideIp	1
imageTypes	jpg,jpeg,gif,png
checkMimeTypes	1
imageMimeTypes	image/jpeg,image/jpg,image/gif,image/png
imageQuality	80
thumbHeight	32
thumbWidth	32
hideUserProfileInfo	put_empty
boxGhostMessage	0
userDeleteMessage	2
latestCategoryIn	1
topicIcons	1
debug	1
catsAutoSubscribed	0
showBannedReason	0
showThankYou	1
showPopThankYouStats	1
popThanksCount	5
modSeeDeleted	0
bbcodeImgSecure	text
listCatShowModerators	1
lightbox	1
showListTime	720
showSessionType	2
showSessionStartTime	1800
userlistAllowed	0
userlistCountUsers	1
enableThreadedLayouts	0
categorySubscriptions	post
topicSubscriptions	every
pubProfile	0
thankYouMax	10
emailRecipientCount	0
emailRecipientPrivacy	bcc
captchaPostLimit	0
imageUpload	registered
fileUpload	registered
topicLayout	flat
timeToCreatePage	0
showImgFilesManageProfile	1
holdNewUsersPosts	0
holdGuestPosts	0
attachmentLimit	6
pickupCategory	0
articleDisplay	intro
sendEmails	1
fallbackEnglish	1
cache	1
cacheTime	60
ipTracking	1
rssFeedBurnerUrl
autoLink	1
accessComponent	0
statsLinkAllowed	1
superAdminUserlist	0
attachmentProtection	0
categoryIcons	1
avatarCrop	0
userReport	1
searchTime	365
teaser	0
ebayLanguage	77
ebayCertId
allowChangeSubject	1
maxLinks	6
readOnly	0
ratingEnabled	0
urlSubjectTopic	1
logModeration	0
attachStart	0
attachEnd	14
attachmentUtf8	1
autoEmbedSoundcloud	1
emailHeader	media/kunena/email/
userStatus	1
signature	1
personal	1
social	1
plainEmail	0
moderatorPermDelete	0
avatarTypes	gif,jpeg,jpg,png,bmp
smartLinking	0
defaultAvatar
defaultAvatarSmall	s_
quickReply	1
avatarEdit	0
activeMenuItem	Forum-Menu
mainMenuId
homeId
indexId
moderatorsId
topicListId
miscId
profileId
searchId
custom_id
avatarType	1
sefRedirect	1
allowEditPoll	1
useSystemEmails	0
autoEmbedInstagram	1
disableRe	0
email_sender_name	info@
display_filename_attachment	0
new_users_prevent_post_url_images	0
minimal_user_posts_add_url_image	10
utmSource	0
emailHeaderSizeY	560
emailHeaderSizeX	560
moderator_id
profiler	0
pickup_category

| Kunena integration settings:

Warning: Spoiler!

Kunena - Finder Disabled
 Kunena - AltaUserPoints Disabled
 Kunena - Community Builder Disabled
 Kunena - Easyblog Disabled
 Kunena - Easyprofile Disabled
 Kunena - Easysocial Disabled
 Kunena - Gravatar Disabled
 Kunena - JomSocial Disabled
 Kunena - Joomla Enabled:  access=1  login=1  
 Kunena - Kunena Enabled:  avatar=1  profile=1  

| Joomla! detailed language files installed:

Warning: Spoiler!

Joomla! languages installed:
de-DE	German (Germany)
en-GB	English (United Kingdom)

Third-party components: None

Third-party SEF components: None

Plugins: None

Modules: None

Not beging able to login seemed to be due to the debug mode. After deactivating this, it now works again

:
Deprecated: strpos(): Passing null to parameter #1 ($haystack) of type string is deprecated in /homepages/11/d653729544/htdocs/libraries/kunena/src/Layout/ on line 272
  (1 versteckt )

I cannot reproduce this error. What happens if you test it with the default Joomla template Cassiopeia? Can the users then also not create topics?

Oh, the whole page is designed for Helix 3. Changing the template is not a thing that could be done after lunch on Friday.