Most hosting providers set limitations to the PHP memory for running applications and scripts.
“Upload_max_filesize”, is an error that displays when you upload a file that exceeds the size limit set by your server. This error can stop you from uploading any media files or installing any theme or plugin on your site.
You can simply contact your hosting service provider to fix this issue.
Other than this there are mainly three ways you can fix this issue.
You need to increase the maximum upload size value in any of the above-listed files. You can also refer to the article guide here for more details: https://www.wpbeginner.com/wp-tutorials/how-to-increase-the-maximum-file-upload-size-in-wordpress/
Note: If your site is on a shared hosting then modifying these files may not work and it is highly recommended to contact your hosting service provider to fix the issue.