Hi.
add dedicated servers to grounded. so that 40 people play in one session (1 session = 40 people).
add co-op pve missions for 3 people (sometimes outside the map).
also pvp mode for 10 people (5 vs 5).
solo quests with a different storyline, sometimes outside the map (an interesting location with different enemies).
pve and pvp modes are common (united) for players of all sessions. make clans if possible.
clan wars in pve and pvp modes. clan players are awarded clan points. total points are summed up.
chat for session, friends, clan and region chat (one language, one region).
quickly translate the game into Russian language. the game was popular in the CIS. This is a large region who knows Russian language.
pure survival genre = low popularity. you need to mix it with other interesting genres and mechanics.