The new mangers just placed a new hotwater tank in the apartmet building I live in and I get really hotwater in the kitchen and in the bathroom sink why don't I get any hotwater in my shower its just warm and sometimes it goes freezing cold when I take a shower for more than 5 minunets.

It is likely their fault and you should tell them that they screwed up your valves which are likely plugged with some debris. We could help you try to fix it yourself but it really is their responsibility. You probably aren't the only person to have a problem due to their work.