can you correct my mistakes?
(Motivation letter, where you shortly describe,how the scholarship for summer courses would complement your Estonian studies). I became interested in the Estonian language a year ago, and have been studying it for more than a year. In the previous semester we also had literature classes, where we’ve learned more about many Estonian writers and read poems and excerpts from novels. Besides our classes I also read a novel and watch films and learn many new words in this way. I am very interested in Estonian and other Finno-Ugric languages and would like to translate Estonian literature into Ukrainian in the future, so that it becomes better known in Ukraine. I’ve already participated in Tallinn summer school and I improved my skills a lot through the classes and communication. This year I’d like to achieve an advanced level and I believe that this course will help me greatly.
I wouldn't say I became interested a year ago and have been studying more than a year. Why would you begin studying it since before you became interested in it?
"In the previous semester we also had" -> Last semester I also had
"Last semester" sounds more natural, and you want to keep the subject "I".
watch films, learn many new words - make these past tense, for consistency.
I would make those changes to start with, and then edit some more.
Is the 'advanced level' you speak of a qualification?
If not, and you are trying to say you would like to become better at Estonian I would probably say something like 'This year I would like to be able to use and understand Estonian at a more advanced level'.
If you are talking about not just improving your Estonian but in a sense 'mastering' the Estonian language I would probably say something like 'This year I would like to be able to gain proficiency in Estonian'.
Second point I noticed:
"I’ve already participated in Tallinn summer school"
Seems like the object is missing here. Additionally, the verb choice is somewhat clunky, though not technically incorrect. Better alternatives could be:
"I've already participated in summer schooling in Tallinn."
"I've previously studied at a summer school in Tallinn."
Or, if Tallinn Summer School is the name of the school:
"I've already participated in a course / courses at Tallinn Summer School."
"I've previously taken a course / courses at Tallinn Summer School."