You probably can't restore a truly "uninterrupted" forest in Europe, as you said people live in most places now and there isn't much you can do about it.

Having said that - Europe's forest coverage is increasing rapidly[0], and growing every year[1].

For another example, UK's forests are already up to "medieval" levels, and growing[2].

[0] https://www.washingtonpost.com/news/worldviews/wp/2014/12/04...

[1] https://www.weforum.org/agenda/2019/07/forest-europe-environ...

[2] https://www.thetimes.co.uk/article/woodland-back-to-medieval...