Hi, I would like to develop a videogame similiar to the old Pizza Syndacate. I have some experience with SDL2. Any suggestions? Where to start?

You'll need to know a programming language, and some graphics eventually.

You didn't state what programming language you used, SDL2 is typically used with C or C++. If you know that language, that will work.

You may also want to have a look at Python and pygame (which uses SDL). As far as I know, the Pizza game is a tycoon-ish game, where you don't have much real-time requirements.

It is generally recommended to start with a simpler game, like pong, tetris, or breakout, to get to know the programming language better, and to get some experience with writing games. may be helpful.

I already made a shooter/platformer with SDL2 and C++. Probably I'll switch to Python to be faster and to not mind about memory allocation.

Great.

Programming shouldn't be the biggest hurdle then.

Can you explain what kind of suggestions you need then?