New site comes up, need a few advices

Hello,

We done new version of our portal site. Site have a huge database of news articles, reviews, comments etc...

1) If we just replace current site with new, maybe Google decrease my rank for some keywords which we build a long time.

2) If we leave two sites (new on subdomain) Google will see duplicate content

3) Maybe is best that I archive old news and keep them on old site and start writing new on new site. Once when I just leave new site, I'll archive old news and put then on subdomain.

3) What to do with multilanguage versions? Is it better to put subdomain like de.domain.com or domain.com/de or maybe domain.de ?

Please help me with this questions because we must upload new site asap. Thanks!

When you have built your new site, do not forget to add links from your old site to the new site. It just passes on some PR juice and may help you get indexed by the search engines faster

Sure, the content will stay the same as on the previous version.