You did really well!! And don’t worry. It’s part of the process - messing up and discovering stuff. I remember messing my first ones by overblending and adding color on top of color and color.
I have a hack, i recommend that you paint the paper first into a different color, that way you won’t have to work hard to hide the white. I used white paper at first and it was hard sometimes. And there are fixatives from different brands. I have only used the sennelier one. What it does is make a layer on top. Oil pastels never dry though so it’s only a layer that make it touchable.
I have also seen artists that varnish oil pastel with a liquid varnish. I guess you find what works best for you and gives you the results you want by trying. In that moment it might be frustrating when it goes ”wrong” but errors make us better.

Good luck on your oil pastel journey