My e-commerce website is 10 years in the internet already, focused just on my home country (.de) and I use just one main .com domain. Now I want to expand to other market (UK) so I want to add new localisation for this market, and use subdirectories do divide the content. So for the new market the url will be: mydomain.com/uk/ and the hreflang="en-GB". Now I'm not sure if for my current country I should leave the main domain unchanged (mydomain.com) and just add: hreflang="de-DE" or maybe it is better to add the subdirectory also : mydomain.com/de/ and redirect (301) all the traffic to this url by default? I already have some authority and position in google search, so not sure if changing the main URL for the website and redirection will have good or bad impact to my SEO?