TL;DR:
Passing through University
I think, most of us - not all - have gone through University. Other have gained experience in other ways.
What I would like to have, is some help.
I think I'm not the only one stressing the upcoming semester in September. I have fallen back a lot with courses like Math and generally lower level stuff.
What is the way of getting there? I am willing to put a lot of work in, but I'm concurrently working few evenings in the week. I don't want to add, that I have problems concentrating, even if that's the situation.
I am talking about Bachelor of Computer Science
Slow down
It's not a race and taking an extra year or two in school isn't that big of deal long term. I ran into a bunch of shit during college, including bouts of depression and the death of my father, and the worst thing I did was try to power through it and worry about graduating in four years. A caveat: It may be a little easier for me to say this than for some others, as my father was very successful in business, so another year or two of college was not a financial burden.
A fun trick: if the classes you struggled in have large lectures, just attend it again the next semester. No one is taking attendance. You'll just be there to learn without having to worry about any of the work or the tests. I did this with a couple of my CompSci classes and it was helpful.
Your school also likely has a bunch of fairly nice people who work in the guidance center who would be happy to talk to you about your struggles and concerns.