If it won't lift and forces itself into the runway your wings ar too big, or positioned in such a way that they mess up the flight

If it flips end over end backwards then you need to put weight in the front

If it leans to one side for no apparent reason, mirror the plane, and try try that.

@Matt7709 https://www.simpleplanes.com/a/0D35L7/A-jet

Ok I'll tag you@Matt7709

@Baldeagle086 do you think you can private upload it and send a link so i could look?

Thx I tied some of these but so far it tips to forward or backwards and have to keep my hunger on pitch. Als every time I roll it spins out of control@Matt7709

For faster planes having the CoL further behind the CoM can make a jet more stable, basically the faster the plane the more you have to move back the CoL to make it stable in turns. But this means it's less maneuverable. This also depends on wing area and weight, for example a light plane with a large wing area can turn very well since the wings will help change the direction of flite way faster then, lets say a heavier plane with a smaller wing area wont turn as fast cause the smaller wing cant change the momentum of the weight. this can lead to your plane pitching up and down in turns, and if your making a fighter this is not very good since you may even get slower turn speeds and lose a lot more speed than normal.

I will make some example planes and link them for you once I get home in about a hour.

I love helping people, I hope this helps!

p.s. if you don't know what CoL and CoM is here you go.
CoL - Center of Lift
CoM - Center of Mass