@nadyart Hi Nadya! I'm nowhere near the level you're at so I don't feel I can really help you with your first few questions but in relation to your last comment on finding time to practice while working on your professional work, I feel I can maybe add some value!
I have a full time job completely unrelated to art and it's been hard to carve out time every day to dedicate to drawing practice. What I've been doing is setting a time target for myself (at the moment it's two hours a day) but instead of focusing on getting a two-hour chunk of spare time, I will practice whenever I get some free time. My two hour practice session could be made up of lots of 20min chunks, for example. It took me a while to get into the habit of just picking up my sketchpad and pencil whenever I had some spare time but now after two weeks of making myself do it it's become automatic.
Maybe you could adopt a similar approach around your professional art work? Maybe take a 1.5hr lunch break and dedicate 30mins of it to practice? And then do 30min practice in the morning as a warm up before you start work for the day? And then another 30min in the evening when you chill?
Hope these suggestions help! xx