My firsts 3D models on sale

I joined in this comunity just 1 week ago and i made two 3D models to start my activity, 

i made these objects in Cinema4D but i provided the .OBJ file for others software it is enough or i need to provide other file formats?

the 3D models are: 

https://www.cgtrader.com/free-3d-models/electronics/computer/pc-monitor--2

https://www.cgtrader.com/free-3d-models/electronics/computer/pc-keyboard

i just want that you rate these objects and tell me if they are well done or if there are mistakes and how i can avoid them. Thank you for the help :D