Lag on final and on the ground (48GB RAM)

Hello, my game starts to lag very much when i want to land (on short final and on touchdown) and at bigger airports e. g. London Heathrow. This happens even though I have enough RAM (48GB). It still uses about 70% of my RAM and it is especially hard to fly in bad weather

Does anyone know what I might be doing wrong or what I can do to adress this problem whilst not loosing much of the graphical advantages, because I know that my PC is capable of this?

My PC Specs are:
NVIDIA Geforce RTX 3060
48GB Ram
11th Gen Intel Core i7-11700KF 3.600 GHz
Storage: Secondary SSD 990 PRO Heatsink 2TB