[2020] Замедляется время в игре

This is completely normal and expected to happen as the city grows. The more citizens you have, the more calculations the CPU has to make. At some point our CPUs (even the most powerful ones) just can't do all the calculations as fast as they could, when the city was small. So time slows down in the game, so your CPU can keep up.

RAM won't really make much of a difference, if any. You could upgrade your CPU which would mean the slow down would happen later with a larger population. The game is optimzed for a 4-core/8-thread CPU (you have a 4-core/4-thread), so something like a 6-core/12-thread CPU would handle the game and system processes better than what you have now.

You would either replace it yourself or you can get a computer store to put in a new processor for a fee. It's important to make sure it uses the same type of socket as the one you have now, so that it will fit in your motherboard, to make sure your power supply can handle it and make sure to get a cooler that fits it as well (unless it comes with a cooler).