Added Internal site on F5 Webtop, now it mixes user accounts

These kinds of problems can be frustrating. Issues like this where one user logs in and sees another user's info is often due to caching. BIG-IP can store web responses from servers to speed access from users. Normally the web app server sends a "don't store this content!" signal to indicate that it is private, but sometimes this can be trouble with it. Review this article to adjust the BIG-IP's caching:

https://my.f5.com/manage/s/article/K14903

Another caching mechanism exists within web browsers themselves and can lead to similar symptoms. If it's the case that you have two users logging into the *same* browser and they see each-other's content, try to disable the browser's web cache. This Stack Overflow article discusses how to do that:

https://stackoverflow.com/questions/5690269/disabling-chrome-cache-for-website-development

If neither of those is the trouble, your best bet is probably to open a support ticket: https://my.f5.com/manage/s/article/K000090256