It's about the mission "Thank you the bus driver in different matches (7 times)" from the love and war event. I thought it meant jumping out of the Battlebus 7 times (say playing 7 rounds) but I already did that but the mission progress bar says 0/7.
If you press your emote button on the bus (usually the cross below) you thank the bus driver.
I thank you.
Thank you for "most helpful answer" xd ^^