"We always study together."
Translation:Ni ĉiam studas kune.
Because that would make it "We always to study together."
The "to study" is the inifinitive, the form of a verb for talking aobut it: You're not studying (studas), but you're talk about to study (studi).
E.g. We always try to study together. What do you do? We try. That's the action of the sentence; it gets the -as suffix. Next you talk about something that you try: What do you try? "To study together." That's your infinitive, which in English usually starts with "to", and which in Esperanto gets the -i suffix. So: "Ni ĉiam prov-as stud-i kune."