>>717885953>>717885953All comes with practice, and differs between games and characters.
An easy way to learn when to hit is to remember the frame data for specific moves you see a lot, or when you have your opponent in a disadvantageous position. Those are the primary times where you get to press for free. This is where you can learn and utilize your block strings, mixups, combos, etc. This also helps you learn the best moves to start with.
Blocking comes with practice, memorization and generally experience, especially in +R which is insane. It doesn't help the game has strong defensive mechanics. Again, resources can assist with helping on how to handle certain moves you keep losing to on block. And whenever you are knocked down, that's usually when you need to learn to block, as risking taking your turn back could cost you, and the ability to take it back comes with experience.
Anti-airing is a strong defensive tool, and is different amongst the cast. Usually you anti-air on defense even in neutral to stop the opponents approach. GG also typically gives all characters an anti-air with 6P, which is a strong option. Mainly learn how you anti-air, such as on approaching opponents and learn your knockdowns.
Spacing is harder in +R than other games due to speed and axis the game can perform in. But when learning your spacing, it helps to keep in mind that you don't need every hit to lead to full damage combos, especially when starting out. GG is known for it's strong pressure and mixups, so having a simple safe normal leading into knockdown is viable at the start.
Many of the issues stem from you saying you struggle with these issues, so a way to tackle them is to put yourself in situations. Specifically, if you are struggling to get a hit with your starter, you can learn a different combo that leads to you gaining the advantage to put yourself in that situation. Thinking around your issues like that is a better way to tackle the issues.