If you want to level up quickly in Once Human, you can complete the Accept Invitation event in the game. This is a great way to earn experience points and get items.
Once Human INVITATION CODES: How to Get One! (Gather Friends Event EXPLAINED)
The Accept Invitation event in Once Human is only for players who are currently under level 10, and they can accept and redeem codes from players who have passed level 10 on your server. You can meet these players on the game's official Discord server or on Reddit.
Here's everything you need to know about the Accept Invitation event in Once Human.
To complete the Accept Invitation event in Once Human, you need to go to the Events tab by pressing F3, then select the Accept Invitation event and press X to enter the code you received from a player of level 10 or higher.