Longer is wrong in this context?
Saying someone is "longer" than someone else sounds a little awkward in English, imo. The only time I can think of where height might be described as "length" is with babies.
is längre taller or anymore, or anyone or further? I get confused by this app
It can mean taller, anymore, further, and longer, yes. You can usually easily figure out which it is by the context, for instance in the example sentence.