Is there a way to pay the transaction fee with the same asset that I am trying to withdraw? ( paying the fee with the assets available in trading contract )
I am also confused with the fee, why should it be so high? 
Another topic:
When I write comments, this is how it overlaps using it from Safari, iPhone XS 
Not quite yet, but this is high on the priority list I believe. At least it was mentioned in the Upcoming features section of this blog post:
As for the fees being high, you are not making a simple transfer, rather closing a state channel. As a result the fees are higher. Notice however that you can lower them slightly by selecting the “Turtle” speed: your withdrawal will be slower but cost less. A good way to lower fees is to wait for a moment when average gwei is low (20-ish).
had the same problem a few days ago. I came up with 3 possible workarounds:
I used the last option which was to say the least: frustrating. Having to use another exchange to withdraw from Nash channels. 
but it worked
Hope Nash finds a workaround soon!
Good luck
