Update problem

Hello!
I have an error when I am compiling my text file:
======================

! LaTeX Error: File `xetex.def' not found.

Type X to quit or <RETURN> to proceed,
or enter new name. (Default extension: def)

Enter file name:

=======================

At the start I used miktex and everything was fine, but then somehow when I
compiled my project there was an errors, something that cant find package
etc., these errors I somehow managed, but with this error I dont know what
to do.

Also I have a problem with package update:
====================
The operation could not be completed for following reason:
The Miktex web service has rejected your request. Pssible reason: too many
requests arrivig from your IP address.
=====================

Can you please help me with these errors?
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