That looks like mould (fungus) growing there. Have you tried scraping it off? If you do check to see if the trunk there is soft or damaged. Probably your soil is too wet. It's best to water when the plant needs it rather than on a weekly or fixed schedule. Fungus can usually be got rid of by using cinnamon powder. Peat moss isn't good to use in potting soil for these plants. The leaning is more likely caused by the plant having good light from only one side and it's growing towards that light. When you repot it you can set it straight up and then afterwards keep rotating the plant occasionally to make sure it gets light all around.

Hello, thanks for the reply. About your questions : I’ve never tried scraping the mold space off. And for your information, the molding spot isn’t soft, so could it still be mold?

Yes, I'd still think it's mould. There are many thousands of species of fungus, most of the noticeable ones have a large mushroom/fruiting body but the main part of fungus is made up of small hair-like structures that grow through organic matter feeding off it. Those that don't produce the larger fruiting bodies are often referred to as moulds but they're still the same thing. Some only feed off dead organic matter so that even if on the surface of living plants they don't affect the living tissue. So if there's no damage or softness on your plant then it should be okay