If I apply for a full-time course, will I find a job that fits my schedule?
That's impossible to answer really. If it's a job that involves shift work and you can work evenings and weekends, then yes. Maybe a call centre/customer service that requires English and Portuguese speakers? But when will you find time to study? To earn 2,500 after taxes you'll have to put in a fair few hours.
They seem to be the best joice, but what do you think?
I don't have any personal experience of them but having looked on the good old internet (!) they are both respected, well established institutions and seem to have a very good reputation. I note that SGH has a joint MBA with the University of Quebec in Canada and Kozminski offers some masters programmes linked to a couple of English universities. English higher education is very strictly inspected and regulated so any Polish college working with them would have to reach the same standards of quality assurance.
How hard it is to be accepted in these universities?
Another one that's hard to answer! It depends on how many people are applying and how many places are available on the course. If there's competition for places then it would depend on the results you achieved in your Bachelors and your CV since then. But look, it's like this. If an applicant has a first class honours Bachelors that they got two years ago and they've spent those two years travelling or working in a random unrelated job they are less attractive than an applicant with second class honours who's spent the last two years working in the industry.