My video is cropped- and more so when exported?

Think of the Sequence in Premiere as the foundation of something you are building, like a house. If the size or shape of the foundation doesn't match the floor plan of the house you want to put on top of it, bad things will happen.

Absolutely imperative to begin your project with a correct Sequence Setting or everything will turn bad from there.

One thing that often works well in a new project is to drag a video clip to an empty timeline sequence, and Premiere will tell you if the video doesn't match the sequence and will offer to correct that. Or you can right-click a video clip in the Project Bin and select New Sequence from Clip.

In either case, important that you are using the most common type/size of video clip in the project. Don't start the sequence with some random still image that you downloaded somewhere, or the sequence will be sized to some oddball setting that matches the still image which could be far different than "video" should be.

If you video source is vertically-oriented cell phone video, and you wish to deliver as wide-screen video, then choose a 1920x1080 sequence with appropriate frame rate, and you may need to scale and rotate the video source to fit that window, then export as 1920x1080.

Thanks

Jeff