increase upload size wordpress

1. Update .htaccess file

  php_value upload_max_filesize 128M
  php_value post_max_size 128M
  php_value memory_limit 256M
  php_value max_execution_time 300
  php_value max_input_time 300

Change the numbers to the values that you need. The max execution time and max 
input time values are in seconds and might need to be increased further if 
your internet connection is slow.

2. Update wp-config.php file

  @ini_set( 'upload_max_filesize' , '128M' );
  @ini_set( 'post_max_size', '128M');
  @ini_set( 'memory_limit', '256M' );
  @ini_set( 'max_execution_time', '300' );
  @ini_set( 'max_input_time', '300' );

reference : 
https://help.servmask.com/2018/10/27/how-to-increase-maximum-upload-file-size-in-wordpress/