the screws on the back dosent fit into the hole as well as other parts being difficult to assembly

One of the chairs is missing the back cover and screws

During assembly, it was missing a screw.

Update... the diagram appears to show the wrong screw

It was not a critical screw for functionality, but without it I could not complete the assembly until I go to hardware store and purchase a screw to install the backrest post bellow.

I recommend that you photograph the stages of unpacking in case there's, for example, a missing screw and you have to try to fit it all back in the box.

2015.The first chair they sent was missing a screw