Pretty good. I like how the dark elf looks but she looks too small compared to the guy judging from how huge his hands are to hers.
Smooth, reasonable models (females look girlish, males look masculine, etc...) Her facial expression works (you'd be surprised how much this is failed)... And you managed to make her seem 'soft'. You might've only really focused "squash and stretch" about her breasts, but being their size and position (near center of attention on screen) works for you here. In theory, her whole body could use a little more foregiveness, a tiniest hint of jiggle as she's bounced around... And she should forgive a bit as she's being penetrated and stretch the tiniest bit as he withdraws.
To illustrate, for her boobs, you can tape a couple water balloons next to each other on say, a board or other mostly flat surface. Then rock the board back and forth for the up and down motions to watch as the water balloons move and interact with each other. It shouldn't take long, and you get two water balloons you can throw at someone (even if you intend to throw at me)
To see what I mean about her crotch and penetration, just look in a mirror and stick your finger in your mouth. Purse your lips (yeah, girls are tight) and watch as you push your finger in and out. That's sort of what you want to imitate on her in animation. It doesn't take much (and too much tends to look either gross, unnatural, or both) but I believe in you. You're solid as an artist and animator, so I hope this can help you :)
Finally, it's good stuff. Breathe, relax, watching a little (or a lot) of porn won't hurt. Keep it up.
4 seconds is not an animation, bro.