A while ago, I bought a Remote Control Plane. Its the Wilga 2000.
I have crashed it and repaired it quite a bit and now its too heavy to fly. It wont take off and when hand thrown it quickly comes to the ground.

Is there any way I can make it lighter again or convert it into something else?
I wish to take up recreational model flying again. I enjoyed it.

Also, I have had to buy a new motor for it because the small gear was slipping.
I'm very sure it isnt the hardware being a pain.

Thanks in advance.
(Serious answers only please)