Hard trigger in ESA 150 Sports Air Rifle

[Dvnshu]

My cousin recently bought the ESA 150 Sports Air Rifle without any research just for plinking. When I tried it, I noticed that the trigger was hard enough to operate with a single finger and due to the pressure needed to apply, the aiming wasn't stable. I asked him to return it but the seller won't take it back, he said.

Is there any way to make it an ease?

Also, the peep sight was not proper(I guess).