I'm a scientific science (1) student. My (2) English (3) level is not very high (4), but I want to improve it because during my studies, I could go abroad I can study abroad (5) if my English level is satisfactory.

1.  "Science student" is equivalent to "student of science."

"Scientific student" sounds like you're describing the type of student you are and not your area of study, i.e.:

exemplary student

excellent student

terrific student

2.  Independent sentences must be separated with a period, not a comma. 

[] - independent sentence

[] - dependent clause

I'm a science student. My English level is not very high, but I want to improve it [...].

Dependent clauses cannot stand alone. If you want to connect two independent sentences, you must use a conjunction:

I'm a science student, and my English level is not very high.

3.  Languages are proper nouns and thus should be capitalized. 

4.  'My English level is not very high' makes sense, but sounds a little weird. Instead I would pick one of these:

My English is not very good.

I'm not very proficient in English.

I don't speak English well.

5.  I just simplified this last part for you.

Without all of the edits:

I'm a science student. My English is not very good, but I want to improve it because I can study abroad if my English is satisfactory. 

Good luck with your studies :) Hopefully you can study abroad! In which country would you study?