Hi guys,
Thank you a lot for the information.
@Allan - I tried the drivers from the link you gave me, selected right OS etc. but it says, supplied, but I get an error about incompatibility of the driver with the manufacturer (probably dell has made some changes to the original one), but thank you anyway.
@Robert - Last week I sent the ticket to Dell as well and waiting for their answer. So far, I was using Dell system update utility which downloaded the latest video driver of the same version you provided me the link for (both versions are 10.18.10.3277). Nevertheless, I downloaded the driver manually from the link you provided me and after restarting it seems to be working.
However, I had this state before that it worked for a few days and then it started doing the same mess. I will test it till the end of the week and update you then. Hopefully this is the solution and the problem was to perform the update over that Dell update utility.
Thank you very much for your help and I will let you know at the end of the week (and mark the answer).