Would mind adding this in your wp-config.php located at the root directory of your site.
define( 'WP_MEMORY_LIMIT', '256M' );
define( 'WP_MAX_MEMORY_LIMIT', '512M' );
You can add it before the line
/* That’s all, stop editing! Happy blogging. */
Here you have a video tutorial in any case:
Let us know how it goes.