If you liked something at first, it means you liked it in the beginning or you liked it the first time that you did it or had it. If something is difficult at first, it means that it was difficult in the beginning. Maybe it got easier later.

起初, 刚开始

Learning how to ice skate was really hard at first, but I learned pretty quickly.When I saw my uncle last week, I didn't recognize him at first. That's because he'd grown a big beard and a mustache.