Can/should I write my front end code before adding back end functionality?

I’m towards the end of the prototyping phase of a social media app im developing. It’s my first time creating such a big project. I’m about to start coding the UI, but don’t have much experience in backend or know which backend technologies I want to use yet. Should/can I first code the UI, and then as I’m doing that learn back end, then start adding back end functionality? Or would this create some sort of problem down the line? Any advice welcome, thanks!