Problem with translation

Hi,

have such a problem: I want to translate in other language, but after save I get error link under:

Warning: preg_match() expects parameter 2 to be string, array given in /home/klient.dhosting.pl/breneo/amc-gliwice.pl/public_html/wp-includes/class-wp-block-parser.php on line 417

Warning: strlen() expects parameter 1 to be string, array given in /home/klient.dhosting.pl/breneo/amc-gliwice.pl/public_html/wp-includes/class-wp-block-parser.php on line 489

Warning: preg_match() expects parameter 2 to be string, array given in /home/klient.dhosting.pl/breneo/amc-gliwice.pl/public_html/wp-includes/class-wp-block-parser.php on line 417

Warning: strlen() expects parameter 1 to be string, array given in /home/klient.dhosting.pl/breneo/amc-gliwice.pl/public_html/wp-includes/class-wp-block-parser.php on line 489

Warning: Invalid argument supplied for foreach() in /home/klient.dhosting.pl/breneo/amc-gliwice.pl/public_html/wp-content/plugins/ecalypse-rental-starter/class.ecalypse-rental-admin.php on line 4080

Warning: Cannot modify header information – headers already sent by (output started at /home/klient.dhosting.pl/breneo/amc-gliwice.pl/public_html/wp-includes/class-wp-block-parser.php:417) in /home/klient.dhosting.pl/breneo/amc-gliwice.pl/public_html/wp-content/plugins/ecalypse-rental-starter/class.ecalypse-rental-admin.php on line 144

Where is a problem?

WP 5.3.2 | PHP 7.3

The page I need help with: [log in to see the link]