It depends on why you write. If you have fun writing, and write just for personal enjoyment, then continue; But i recommend just not posting it in that case. No point in posting something you believe is bad.
If you write to have it seen by others, then you should polish your skills first, then start writing. But you must understand that the first thing you write will always be garbage. The second thing will be slightly less garbage. And so on. And I'm not talking about your first story, I'm talking about everything: your first draft will always be of a lower quality than a second or third or tenth, in part because you gain experience as you write and in part because you have the benefit of the previous draft to make clear what worked and what doesn't.
This is one of the two biggest consistent threads i see among low quality works in this site: lack of editing. Most seemingly just write a chapter, don't re-read or edit or sometimes even spellcheck it and that's it. No wonder it ends up low quality: quality costs effort, and they've barely put any.
Just for the record, the second biggest consistent thread of low quality is short chapters(generally around 1k words or less. SPECIALLY less.) this has to do with pacing, and is not in the scope of this discussion.
TLDR: write if you want, but i recommend you don't post it unless you have at least a little confidence in it's quality.