"The nextbots don't died correctly :("
Make sure you don't have incompatible addons, the half-life 2 snpcs by example, has a file that breaks nextbots, if it isn't from that addon, check the console (usually with F10) and send the error in the bugs thread

"They don't move besides sideways"
Make sure you are playing on a nav meshed map, if there isn't any, you can generate one, in console put "nav_edit 1"
aim at the ground
"nav_mark_walkable"
and now use nav_generate
it should be navmeshed when the map restarts.