Difficult moments in passing (Metro: Last Light)

Inspired by missions on the Swamp and in the Catacombs. Before that, the game was very easy, especially where it was necessary to resist people. But Bolt had to run very well and in the end, there were not enough filters in the place where the boat sails, had to reboot the mission. Well, I think that's it, now the mission will be easier, in the team. And no, again monsters and... now there is a shortage of ammunition. In short, two rounds for the Bastard, 80 for the machine gun, a couple of grenades, knives and first aid kits. And the monster boss is against me. In general, where is the trainer for unlimited health?...

And what were the difficult moments for you?