It sounds like you are "fit" on the client side. If you want to start programming the part on the server side, I would propose to study "data modeling" first. If you do not even know what "entity" means, your backend is probably going to a permanent construction site. If you are not able to "design" a good fundament it doesn't really matter what programming language you are going to use. Choosing/switching the programming language is the easy part - in my opinion.