A matter of settings. Under the preview window, use MATCH MONITOR, to give a representation of how the project will look on your monitor. On the cut off scenes, be sure to type the text within the preview image boundaries.
For images/videos that aren't scaling correctly, try applying the Letterbox to Aspect Ratio effect to them. 
In export, you should be able to select the A/R choice.
Upload and share your video and someone will make specific suggestions. This isn't difficult, takes little time and can be private. Just follow these steps...
1. With your project on the timeline, click on MENU at the top-left. Click FILE|BACK UP PROJECT FILES TO FOLDER. Choose a folder and SELECT FOLDER.
2. Locate the saved, numbered folder and upload it to a free server - Google Drive, MS OneDrive, etc.* (Don't upload the export file or only the VPJ.)
3. Get a shared, public link. If using Google Drive click GET SHAREABLE LINK. Click the blue "Change to anyone with the link..." Then click COPY LINK | DONE.
4. Paste that link here, or click the folder, above top-right in this forum, and message it to me. This is private and won't be shared.
* Before uploading, right-click the folder, click PROPERTIES. Look at the File Size to confirm that it's not too big for the free space on the server.
