Why not "for" instead of "til"?

Why do you need til?

"til at" when "to" in different situations without verb,adverb, etc. "at" when there is verb link(prøver at løbe)(tries to run) "for at" - in order to "med til" - at

Why can't it be just at taenke or til taenke

I read "I need time to drink" ....