You can shoot, use grenades and melee attacks. You can carry three weapons at a time and ammo from fallen enemies is gathered individually for each one of them. The first weapon never gives you bonus to "extra" damage - they don't have color icons that grant you damage bonus for certain types of shields. In other words, they are called kinetic weapons, as opposed to energy weapons. However, they use the most commonly found type of ammo (white chests). You should equip an automatic or semi-automatic weapon.
The second slot is for a secondary firearm - here, you will also get a lot of ammo for them (green ammo chests) but not as much. You should use a weapon that is the opposite of your primary one: for example, if you use an automatic weapon with low attack stat then you should select a single shot and precise one as your secondary, thanks to that you won't find yourself in a situation in which you run out of ammo or you don't have weapons for short/long distance.
The third slot is dedicated to heavy weapons (purple ammo chests). It is hard to get ammo for them because it is a rather rare loot from fallen enemies and magazine's capacity is small. Here, you should use weapons that deal a lot of damage (sniper rifles, fusion rifles or swords) or those that deal massive damage (e.g. rocket launchers).
- If you try to use, e.g. a heavy handgun to deal damage at a long distance, that weapon won't be effective. You will deal less damage than a much weaker weapon that has a scope and is suitable for fights at a greater distance (such as Scout Rifle).
- Enemies that sustained a lot of damage don't become weaker or less mobile and because of that you have to be sure that you finished them, especially those that use ranged weapons - they can move farther away from you and cause a little bit more trouble.
- Try to always be at a higher position than your enemy: it is easier to hide, notice enemies that are hiding behind a cover and aim at their heads while, at the same time, it is harder for them to see you.
- There is nothing stopping you from carrying an additional weapon for each of the free slots and choosing those, that are better for enemies that you currently have to face (the currently used weapon can be changed by going to your inventory even during a battle but you should hide behind a cover). You can have up to 9 weapons per each slot which in gives you 27 weapons in total. If you reach that limit then you will have to dismantle something (go to your inventory and press the right button after selecting an item that you want to dismantle).
After completing a mission or a match you can find precision kills as a part of the statistics. This shows how many kills were performed by a precision shot at a weak spot, mainly head or, in case of some creatures, such as robots and bosses, at a specific place like fuel tanks, cameras or glowing crystals on their bodies. After some time you will be able to recognize which enemies should be attacked at their weak spots and how effective that is. When a number indicating damage is yellow instead of white then you know that you hit a weak spot.