Cant access dashboard after move to another URL (and server)

I moved my WP site to a different URL and server by manually copying the files and database, then doing a SQL query

UPDATE wp_options SET option_value = replace(option_value, 'https://www.oldsite.com', 'https://www.newsite.com') WHERE option_name = 'home' OR option_name = 'siteurl';

UPDATE wp_posts SET post_content = replace(post_content, 'https://www.oldsite.com', 'https://www.newsite.com');

UPDATE wp_postmeta SET meta_value = replace(meta_value,'https://www.oldsite.com','https://www.newsite.com');

on the imported database on the new server, and changing the database data in wp-config.php in the end. Everything looks fine on the site, but I seem not to be able to access the Dashboard, returning an error

Warning: Cannot modify header information – headers already sent by (output started at /home/content/b/l/u/bluealek/html/4×4/wp-config.php:1) in /home/content/b/l/u/bluealek/html/4×4/wp-includes/pluggable.php on line 1179

Trying to access wp-login.php doesn’t help either – I get the faults

Warning: Cannot modify header information – headers already sent by (output started at /home/content/b/l/u/bluealek/html/4×4/wp-config.php:1) in /home/content/b/l/u/bluealek/html/4×4/wp-login.php on line 418

Warning: Cannot modify header information – headers already sent by (output started at /home/content/b/l/u/bluealek/html/4×4/wp-config.php:1) in /home/content/b/l/u/bluealek/html/4×4/wp-login.php on line 431

and when I enter the username and password it’s not accepted.

What did I forget to alter in the process of moving the site? How do I repair that now?