Hello Noyd and welcome to the forum!

Your status gets upgraded immediately after reaching 10'000 points, the card will take a few weeks to arrive, but online it will already be visible as gold (and also count as such for hotels, but you might have to convince some of them ).

You keep those 10'000 points of course and can spend them however you want. Once you reach gold status, it will be valid for a year. Within this year, you have to gather ANOTHER 10'000 points to keep your status. So it's always the amount earned within 1 year that counts.