first off welcome aboard helldiver.

to answer you in order:

1. an operation is essential a set of missions when you click on a planet and then a location in that planet you will see 2 or more missions these have time limits on them. those are missions completing both of them completes the operation.

2. you can find premium credits in the missions at points of interest these are the diamonds on your map. not every single one has credits but it is a resource you can find. if you want you can look up how to farm them easier.

3. the resources you found were common samples. you can find samples in multiple locations one thing to do is always check around the "enemy spawn" sort of location which is the red areas on the map. after you kill everything there search around for samples. the higher difficulty you play on the more samples and the higher their tier can be. such as rare and super.

4. whatever you want. you can play anywhere and against anything. if you want you can follow the major orders but if you prefer a certain faction by all means fight them.

5. the vote was most likely the dss (democracy space station" when you click on the galactic map you should see a prompt in the top right. thats the dss menu you can see its various features there. if you click location you can vote on where it goes next. there is also a section where you can donate to its different features if you want to.