There is a lot of work w8ing for you m8 xD I wont critique your drawing because for beginner level it seems decent. However i can tell in which areas you should improve
Study basics:
- Diffrent types dof lines, straight, curves also circles
- Study figure drawing around from 30 mins to hour a day
-Study anathomy: skelton and muscles, for face also facial features eyes etc.
-Study perspective
- Study shading
-Study composition
-Study colors
And even more. Id suggest also buying good books especialy those which Marc ( cube brush ) .suggestedhttps://cubebrush.co/blog/essential-art-books-for-artists
Also you might go for some art classes but i dont know how are those because im self-taught. Study one or two things a the time it will help ya make faster progress, Good luck and the most important have a looot of fun 
