Slowly getting tired of work

Hi there! I've been working as a 2nd Assistant Manager for about a while now, and it's been quite challenging. I haven't received proper training. However, due to the shortage of staff, I'm struggling to keep up with tasks like basket returns, handling freight and transfers, as well as opening and closing duties. We're also short-staffed in the garden center. It hasn't been open for a whole week, and dealing with returns has been a nightmare cuz we don't have anyone to do it and departments throw a fit when we have to make them take care of it. I understand you guys are short, but so are we, and it's only getting worse. We have about all our cashiers leaving within 3 weeks for college and only 2 carry-outs now because our GMs are moving them to different departments. I have been getting nonstop rude and hateful customers towards me and have no one at work to even vent to since they just tell me, "Oh, youngsters, haha." I feel so alone and lost at work. I hate coming to work since it's just a nightmare, and the GMs, every time we complain that we need more people, just tell us we are making excuses left and right. I hate it, I once loved my job and now I have grown so tired and disgruntled. I can't even quit I have bills to pay and also support my family. I guess I just have to find a way to manage somehow in this situation.