Note : TRANSLATE TO RUSSIAN
this is a guide for a user that asked me for help , so that's why it's in Russian

center of mass and lift

The center of mass and lift are the key points of an aircraft and must be stable for the aircraft to operate. If you want to be sure the center of mass (red) must be in front of the center of lift (blue) you can activate the option to see them in the menu

amount of lift and speed

This is a important part of building a plane if you can't generate enough lift your plane won't be able to pull up, but if the plane has a very high speed there's a chance your plane can pull up, but is better to have enough lift to take off without problems
And the speed of your plane can't accelerate enough your airplane won't take off , here happens something similar like before , you may have a lot of lift , and a bit of speed and still take off , but It only happens depending on the measurements
That's why is good to have a balance between speed and lift

maneuverability

So now that you know the basics of a airplane you must know about maneuverability but... what is maneuverability? Maneuverability is the capability of a plane to pull up, down (pitch) turn left ,or right (yaw) ,and roll left or right (roll) now 1st of all

PITCH
This is caused by the horizontal stabilizers at the back of your plane, this allows you to pull up or down
Yaw
This is caused by your vertical stabilizer that gives stability to your aircraft the yaw makes the plane turn left or right on the same plane
Roll
This is caused by the ailerons of your airplane main wings when you roll left your plane tills to the left and when you roll right your plane tills to the right , you can turn using pitch and roll or yaw and roll

That's why you must check your controls!