This is a really cool arrangement! Also I feel you on the never feeling satisfied with the sound in recording. I think you did a good job overall.
The violin is such a good instrument for instant Halloween vibes and the piano accompaniment was really well done.
I would say, if you want to try and improve the sound quality of the recordings, look into mixing plugins like EQs and compressors to tweak the sound to your liking. I know Audacity comes with some built in ones but in my experience, third party VST/AU ones can give you better results. Some free ones that I like are TDR Nova (Dynamic EQ) and MCompressor from Melda Production (The entire free plugin collection from Melda is really good). I think it's really cool that you're trying to get better and I'm rooting for you on your journey😁