First off, well done. Much better than my first game ever, especially in only 5 hours (it was also about slimes, coincidentally). That said, here's that feedback you requested.
This game needs to be better at telling the player things. What does the meat counter mean? How many slimes is a good number? Why am i just standing here? You should make sure players know this stuff. As the creator of the game, who designed everything in it, it can be easy to forget that players might not know what's going on or what those numbers mean. There is a lot of stuff players can usually just "figure out", but generally the better game is the one that doesn't require players to do that.
Again though, these are problems every new game dev has to figure out. I think it's amazing that you were able to get anything out in only five hours with no experience!