I can also support the idea of starting small and building from there. Even if you've got an idea for the whole thing in your head, it's still going to take time to build it out while sharing with others. Start small, discover the world as you make it!
I think it's also important to know the
scope of what you want to build,
before you start working on it in earnest. Are you making something whimsical that doesn't need explanations for every little detail? Or are you intending for it to be a plausibly real place, needing full explanations and correct physics for everything? For instance, I'm making a scifi near-future Earth with space travel and furries, and it's been my intention from the start to make everything plausible. Part of my process has been to define pre-historical geological events and divergent evolution, studying the energy needs for ion thrusters, and detailing food production at high volume within orbital space habitation stations. But I need this background information only because
I chose to make my world plausible. If I only wanted something more fun and wanted to focus on the stories and characters first, I'd not worry too much about any of the science of my science fiction and just get to work writing plots and conflicts. (As it happens, the research is helping me to discover conflicts, like how does a station decide what the weather will be? Or I'll bet there are raiding parties of pirates that attack space stations, but the ones that grow lots of food are probably spared bc you don't mess with food in space!)
Think Star Trek vs Star Wars. Do you want lots of background explanations and social commentary, or just fun magic and flashy whimsical stories? Both are great!
I think another piece of advice I can offer is: as the creator of your world there is going to be so much in your head that will
only ever live in your head! Not everything can (or even should) be shared in your work, and that makes the world more rich for your readers, because (I believe) they can tell when there's more under the surface, and it makes it feel more real. I don't need to share in the text exactly what's going on on Mars, but I can hint once in a while that there's something fishy going on after the Corpo muskrat took his companies and his workforce and founded a colony, named himself king, and began nuking anyone who approaches, and now nobody has heard from them in a hundred years.
I know that Dante's Inferno is happening on Mars, but
my readers only need to wonder what's going on. They make it real in their heads.
As far as language goes:
why yes I do dabble in conlangs! I also intend to study contact languages (pidgins and creoles) to make something for the people of my space ports to speak in orbit. Language is absolutely not something that is necessary and it's enough to write in your native language and simply state in the text that a different language is being spoken by your characters. I certainly don't plan to compose a Corvus phrase everytime my crows are talking to one another!