Signing in/out message.

[xkevin]

What function/code responsible for this? after signing in this message appeared.

[.m.]

if you do not want to see such messages, navigate to below location and turn off friendly redirection pages

forum admin panel >> Configuration (settings) >> General Configuration >> Friendly Redirection Pages

edit: user control panel also has related option for the individual users

[xkevin]

if you do not want to see such messages, navigate to below location and turn off friendly redirection pages

forum admin panel >> Configuration (settings) >> General Configuration  >> Friendly Redirection Pages

edit: user control panel also has related option for the individual users

Thank you for that. But I just want to make a message like this after a (customize) redirection.

[WallBB]

I believe you can modify below template here and put custom message.
Theme Templates »Ungrouped Tempalte> redirect

[.m.]

see redirect function in functions.php file