I will order:
1. copying the site Wordpress theme Ocean WP Pro (license for 3 sites, left for 2). The page to be copied is fmt-cnc.de it is to appear under millingcnc.eu in a 1:1 copy i.e. all plugins, images, properties etc. The millingcnc.eu site before replacement should be saved so that I can later swap the content from non-German to Polish.
2. adding on millingcnc.eu and fmt-cnc.de in the top menu PL/DE/EN language switcher.
3. POLYLANG PRO if it makes sense, or another plug-in, so that the fmt-cnc.de website has an EN version, e.g. fmt-cnc.de/en and as in point 1, copy the German version, in which I will later change the content to English.