Xenomorphs are one of the most agile and hardy creatures known.  As such you get +2 to Dex and +1 to Con.  

A Xenomorph does not posses eyes and as such need a different way of seeing the world.  Most xenomorphs have to ability to use echolocation and some form of Electric Sensing.

Blind Sight 40ft

A Xenomorph is a creature bred for combat.  As such, you have claws and a tail that is used to attack others.  You are proficient in them.  

You get two attacks per turn, one claw attack and one tail attack.  Claws- Dex to hit, 1d6 slashing damage + Str modifier.  Tail- Dex to hit, 1d8 piercing damage +str modifier, reach of 10ft

A xenomorph can move on walls and ceilings as if they were walking on the floor.  35ft of standard movement and gains 35ft of climbing speed on walls and ceilings.

A xenomorph is a very agile hunter.  Proficient in Stealth and Acrobatics.

Your tail acts as another limb.

If any attack would break the skin, they must make a dex saving throw ( DC 8 + Proficiency bonus + Con Modifier) and take 1d6 acid damage, halved on success.   1d6(1st)  2d6(6th)  3d6 (11th)  4d6(17th)

You know xenomorph as a base language and can never speak another language.  You learn language at an accelerated pace and can write in any language you've learned.  You can use Telepathy to communicate with any creature you can see within 30ft.  You do not need to share a language with the creature but the creature must know a language. This telepathy is used to transmit simple and straightforward ideas/concepts.

You take twice as much damage for fire sources.

Xenomorphs are notorious for being fast moving and hard to kill.  Your AC is 12+Dex Modifier