There are various issues you may run into, especially if you have a misconfigured server. The first solution is to increase the PHP limits. You can do this on your own, or contact your web host and ask them to increase those limits to a minimum as below. Please also check WordPress’s official requirements.

max_execution_time 180

memory_limit 128M

post_max_size 64M

upload_max_filesize 64M

max_input_time 60

max_input_vars 3000