how can i imprive my sketching on my own?

See learning any applied art form is always dependent on the practicing of the art form. So to make your artwork more proficient you have to practice a lot. Now techniques matters a lot in applied artwork. So to learn techniques about different sketching techniques you can follow the books written by famous artist as well as online sketching classes. You will find a lot of videos in youtube.

Also you can copy different sketches of anime characters etc in order to compare a framework and the precision you can apply to the sketch.

This are some of the ways you can follow to improve your sketching.

Now if you want to know about the CEED you can visit the link below(if you are asking this based on such exams):

https://design.careers360.com/articles/10-tips-crack-ceed-in-30-days

I hope this helps. All the very best for your future endeavors!