While studying ............ [ name your main subject, eg Economics] at ................... [ name of university] University, I increased my professional knowledge of................., and improved my skills in analyzing and solving problems.

Hey, D! This is how I would phrase your statement - During (my) period of study in university, I (gained) () professional knowledge, and cultivated the ability (to analyze situations, solve problems, and educate myself). Why? Well, you can't really "master" knowledge - with the verb "to master" you can only master a skill. Swimming, fishing, chess, etc. "Knowledge" isn't a specific skill, so you can't really master it... you can cultivate it, expand it, increase it, but not master it. Maybe because it's impossible to know literally everything. :) Secondly, with the phrase "to cultivate the ability", you need to follow it with another verb. Examples: I cultivated the ability to work in a foreign language. I cultivated the ability to travel very cheaply. I cultivated the ability to swim for long distances. You can't cultivate the ability (noun). "Problem-solving" <- in this case, this is a noun. As in "I love problem-solving". You need to use it in a verb form. Hope this helps. (P.S., your initial question - "I want a job,this is a myself- introduce,is there any worse?", would be better stated "I am looking for work, and this is my introduction. Are there any mistakes?" Best of luck in the job search. :))