I keep dying

Exactly which ME aer you playing? becvause you mention the Normandy but the Normandy isn't in Andromeda

Wel if it's ME1 use the tactical pause feature that's always a good idea anyway when firing off powers in that game. Especially if you don't have particularly quick reactions.

Unless you are trying to unlock an achievement for playing on a specific difficulty (such as Insanity), then I recommend lowering the combat difficulty. Drop it Casual if you have to. The lower the difficulty, the less health enemies have and the less damage they deal. So if your finger joints lock up, hopefully the enemies will not kill you before you have a chance to correct the situation.  

Otherwise:
1. As sjsharp2010 wrote, use the tactical pause (weapon wheel or power wheel on consoles) to plan your attack and use powers.

2. Hang back as much as possible. This should prevent you from needing to move around a lot.

In driving sections, you can kill enemies using the Mako. Use the terrain to your advantage to avoid fire and then fire back. You can scope the Mako up to 2x zoom, letting you shoot enemies from afar.

For indoor sections, stay behind cover. Indoors, you can open doors and just stay outside shooting from relative safety. There are a few segments where you are kind of forced into getting surrounded by enemies, but you can usually try to kite or lead enemies into a straight line in front of you.


Hopefully this advice helps somewhat.

As for finishing a mission:
1. On uncharted worlds, you need to be in the Mako to exit the planet. Alternatively, you should be able to exit the planet from the map whether you are in the Mako or not. You should be able to access the map from the pause menu.

2. On story missions, you typically need to complete the entire mission; there is no end button. Eden Prime, Therum, and Virmire require you complete the mission before you go back to the Mako. On Noveria, you can head back to the Normandy at any time although it can be a long trek back. on Feros, you can head back to the Normandy at any point until you drop down a specific point in Exogeni building (just inside after you finish the skyway); after that point you must complete the mission before you go back to the Normandy.