Clip imports zoomed in and when resized to normal, quality is very low.

Sounds like your sequence settings might be smaller than your clip settings!

In your project window, find your sequence and you can scroll to the right to see the size of the project (here my project is 1920 x 1080). Alternatively, right click on the sequence > Sequence Settings > and it will tell you the frame size in the Video section

Same process to check the size of your video files:

Check that these two sizes are matching, it sounds like your video files might be a lot larger than your sequence!

Fastest way to correct this is you've already started editing:

1) Start a new sequence.

2) Drag one of your clips (that is of a standard size) into Premiere it should pop up with the following window:

3) Select 'Change Sequence Settings' and the sequence will then perfectly match your clip. If you've been working away on the other project then you can copy and paste them in, which will paste them in at the correct resolution.

If that window doesn't pop up, start a new sequence and you can choose your frame size from a load of presets (if you're new to this I'd recommend starting in the Digital SLR folder and choosing 1080p or 720p)

Hope that helps!