It is very difficult to give any sound advice in a few lines.
A lot of people out there just wanted to hit the ball as hard as they can, but never knowing how to do it properly. (I have seen people hitting every ball with an underarm stroke and sent the ball high up in the air. The ball will stay in alright but she looked more like playing badminton stroke to me. )
My two cents, the best way to improve is always getting a coach to tell you what you have done wrong.
See this introduction of forehand. You need the following :
1. ball sense, get to the right position and swing the racquet to hit from low to high;
2. grip the racquet too tight cannot swing smoothly and control the power, swing softly and keep you wrist firm when touching the ball. Contact points are always the same in your front right. Face where to hit the ball, ball would goes to the destination.
3. time of contact only 0.004 second, watch the ball contact your racquet, don't move you head until the follow through swing completed.
Well, if your racquet head face up at contact of course the ball is going to fly up.
But then I don't know, I hit flat stroke so.... if u hit flat, u will have to take the ball on the rise at top and do not close racquet... just have your racquet head parallel to the net, it will go over the net!
Regarding to the angle thing. it really see where is your shoulder is pointing or how early u take the ball. For flat stoke, it is entirely depend on your shoulder rotation and where is your shoulder is pointing at ball contact. If you take the ball early, your shoulder is more of less pointing at cross court position and therefore cross court shot and if you take it late and your shoulder is pointing at the straight line position, you are likely hit down the line
Ar one thing, don't overpower, remember you are playing tennis not playing Grand Slam, you don't have to hit winner after winner. Sometimes, just keep running ball down is more fun and hit until the other side make an error is more fun than trying to hit winner from impossible position or when you do not have the skill enough to do so, just a slight pointer