@DrPanda I fixed it adding dead weight on the nose. it does not spin again. nice tip

Thank you guys for the help!

@gokay01 i hope this will not disgusted you if you want i can remove the post but firstly look at that.

İ downloaded and i find the issue. İts so easy, center of mass. You need to slide your wings back only. İf you want the see modernised type look my profile thx for this nice building.

I downloaded and found the issue. So basically in an aircraft, you want the center of mass to be in front of the center of lift. However this is not the case in your plane, and it makes it very unstable and simply inflyable. Fix the issue by removing the fuel from the back of the plane and if necessary add some dead weight in the front.
I dont know if you know that, but you can display the different force centers (mass, lift, thrust) by going in the left menu and pressing the button with 3 circles and a triangle.
I hope this helps 👍, and good luck in your plane designing journey.

Edit: you'll also find plenty of tutorial on youtube for simpleplanes

please tell me