What do you do when you have an idea in mind but no clue how to dev the front end?

I can do the server and backend but zero knowledge on how to begin the front end.

Mind you, I know front end dev pretty well and have made lots of projects on my own. What I’m referring to here is complex UI/UX implementation.

I don’t mind learning new things but I doubt I can make things look and function like I’m dreaming.

Any thoughts on where to start with this?