Your project went well in 11.17 (32-bit), after about ten minutes to let it fully cache.
Allow the blue bar (ribbon) under the preview window to turn purple. It may seem to hang for several minutes. Have patience. 
Once that's done open OPTIONS | DISK tab and Clear Unused Cache Files. Do this before beginning a new project, but not when reloading the same project last worked on.
You should get better results with a 64-bit release. Here's a beta to check out.
If things still bog down, break up the project. Export the partial project, which will become a single file. Restart Videopad and clear the cache.
Continue with the new segment. When complete, export it as well.
Lastly, begin anew and import the exports into a new project which is then a simple assembly of a few clips. Export the final.
In any case, Save Project File AS routinely, giving it a unique # or name, so as not to overwrite prior saves. Using Save Project Files (no AS) will overwrite. From the HOME tab, that choice is available by clicking the chevron to the right of the Save Project button on the toolbar.