Bandwidth gets limited after setting up L2TP tunnel

Hi, I have 2 Mikrotik routers, after setting up an L2TP or any tunneling my bandwidth gets limited to my Windows PC. BTW there is no bandwidth limit in any queues, I have 50mbps in one router and 150mbps in another router. When I connect with any tunnel in my Windows PC the bandwidth limits to 20mbps, but without any tunnel my bandwidth is fine. What is the problem here? can anybody tell?

Crystal ball, crystal ball, what can it be ??

Most likely explanation would be that everything is being send over that tunnel once it has been established.
Without seeing config or setup of that tunnel (on your PC ?), nobody can tell.
Please also add small drawing clearly indicating how all pieces fit together in that setup.

ok, giving some info in pics
l2tp connected.png
wifi connect without l2tp.png
speed test without l2tp.png
speed test with l2tp.png
queue.png
windows setup.png
l2tp 2.png
3.png
pool.png
l2tp setup1.png