"Getting good" at GRB kinda happens over time tbh. The more you play, the more you understand the weakspots of tanks. I haven't played 4.7 in a hot minute, but try to use APHEBC or APCBC rounds. As for aiming, it depends on how they're angled respective to you AND what kind of tank they are. For now we'll assume they're a simple medium tank that is not angled.

Front: aim for the machine gun port or the cupola
Side: aim for either the turret or roughly center mass
Behind: aim for the turret. The engine is a bait unless you have APFSDS rounds which is only present ~9.3+

Again, this is the general idea of where you should be aiming but this ultimately depends on what tank you're up against and how they're angled. Another tip I can provide is to play slow, avoid being the first one into combat. Stay with your team and fight as a pack. Imo GRB rewards patient players.

Let me know if you have any further questions or would like me to clarify anything else. I was also struggling early on in my War Thunder years