Simplify the following text for a Grade 13 native English-speaking person.
Original: In the first Half-Life , the player , as Gordon Freeman , fights through the facility alongside fellow employees , engaging the aliens as well as a military unit sent in to contain the situation and silence any surviving witnesses .
Simplified: In the first Half-Life , Gordon Freeman , fights through the facility with other workers , fighting the aliens as well as a military unit sent in to stop the incident and silence any surviving witnesses .