I cannot upload files larger than X mb

Adjust PHP settings to allow uploading large files:
- max_execution_time: max execution time of scripts (Suggested: > 300)
- max_input_time: max execution time of upload (Suggested: > 300)
- memory_limit: not equal to post_max_size or upload_max_filesize (Suggested: > 512M)
- post_max_size: the maximum size of the file you want to upload (this value need to be larger then upload_max_filesize)
- upload_max_filesize: the maximum size of the file you want to upload

If you are under NGNIX server you need also to increase the client_max_body_size to the same or greater value of post_max_size.