How to brush the research card of the king's guard sentry in the crossfire gunfight

Biochemical Hotel jumps over the iron gate (there is an iron gate on the far left of the map). There are two ways to get on the iron gate, one is to punch in by Xiao Long, and the other is to take a ladder. Then someone catches you infected and walks into the void (that is, the boundary of the map) and will die forever. You can gain a lot of experience by scoring a point in the second round.