The 16 hours of course was only a part of it, where the teacher talked about fundamentals and i asked to them in my excercise to show what they've learnet about that. Two of them are out an IT university, the other two claimed that they have programming fondamentals, at the end when i said "open PowerShell", some of them ended up searching for it in google.. So at this point i can claim that they lied in the interview and that was the point why the company hired them, now i have 4 people i have to teach programming while i have lot of projects to mantain and develop..

Then you should edit your original question to better reflect the facts. Remember that we can only answer based on what information you provide.

The non-English speaking hire was probably hired through the affirmative action program. Thus it would be illegal to fire this individual as they would be a protected class. Unless policies change at the national level, the OP is stuck with this deadweight.

@jwh20 you're rights, added the new data about trainees and course in the question

@Jack even the non-English speaking was hired after an interview and has claimed that his technical english is okay so there are no issues about firing or other stuff..

"Two of them are out an IT university" - Unless they had a course in Java Script this means nothing. I could literally program anything you want in C, C++, C#, Java, or even Assembly but if you want something in Java Script I would look at you with a strange face. Sounds like these individuals know nothing about Java Script. I have a BA in Computer Science and a BA in Computer Engineering. I have written 0 lines in my nearly 20 years of programming.

@Jack How is it affirmative action to hire someone who only speaks Italian... when you are in Italy ?

@user3067860 coz italy is full of migrants?

@Frank So it's affirmative action to hire a local because they're so hard to find, the gov't actually has to incentivize hiring native people?

@user3067860 what makes you think this migrant who only speaks zulu and italian is native?

@Frank OP says, "he translated some code or docs from English to native language" and then "nowadays he translates all docs or code blocks from English to Italian"...and the tags say Italy and the OP has marked their location as Italy. So you have a native Italian speaker in Italy, but the workplace language is English.

Simply asking: "Do you have any questions?" is almost always ineffective in my experience. This times a billion. The fact that the actual teacher is doing this is a red flag about the quality of the rest of the course, in my opinion. You cannot ask someone who doesn't realize they've misunderstood something whether they understand; of course they'll say yes!

Absolutely. Answering "no" to "Do you have any questions?" means "I can't think of any short question right this second, to which a short answer will help me". It doesn't mean "I think I understand everything". Just composing a question about topics that are very new and you barely understand is actually really hard. It's not something people can do usefully in the sort of short question period you get in the middle or at the end of a class, while also having the disincentive of feeling like they'd have to put their ignorance on display for the whole class and hold up proceedings.

@BSMP "Do you have any questions?" is often heard as "Are you really that stupid? Did you pay attention to anything I said?"

"Any questions?" can also be a code word for "These are my orders, now get to work!"