It is necessary to prescribe a rule which would redirect from all pages in the category old site to a certain category, while cast would all get requests of the old site.
Now there is a rule written in. htaccess of the old site
RewriteRule ^brands/ https://new-site.ru/manufacturers
RewriteRule ^(.*)$ https://new-site.ru/
it correctly redirects in this case : old-site.ru/brands/Sony on new-site.ru/manufactures
but when you request old-site.ru/brands/Sony?newprice it turns out new-site.ru/manufactures?newprice
u need to new-site.ru/manufactures no get request.