Are you allowed to go in a hindu temple if you're catholic?

Hindu's allow it.

You can but Christianity forbids worshiping other gods, which is what Hinduism is, so a Christian should not participate in other religions rituals.

This is a very non-specific question, so I'll have to give a broad answer.

Yes, except when you aren't.

See, it's a broad answer. To get into more specifics, there are a variety of things to the situation:

Are you participating in religious rituals? If yes, then it is a sin.

Are you weak in your faith (that is, could you be converted in that place)? You have to be honest with yourself on this one. If yes, then it is a sin.

Those are just two broad points, but there's a lot more nuance to it than that, despite what a certain non-Catholic who has commented before me is trying to tell you.

You might want to be careful. Some observances of theirs
include nudity. Not joking.
So if your Catholic beliefs permit your seeing nudity, you're attending would not be a problem.

No dont go if you're catholic its a sin