Catalina installer not responding

Press and hold down the Power button until the computer shuts down. Wait 30 seconds then reboot. Are you able to reboot, does the installer pick up where it left off, or are you returned to your old system?

I will point out that 19GBs of free space is insufficient to complete an installation. You need at least 20GBs during the installation as well as normal free space needs of another 10-20GBs. The installation may have stopped, possibly, because you ran out of disk space. If you are unable to restart the computer, then that is what happened. If you are able to restart to your old system without any problem, then you got lucky.

Let me know where you are, now, so I can help you get this done. But you will need to free up some disk space. See the following:

How to Free Up Space on The Hard Drive

1. You can remove data from your Home folder except for the /Home/Library/ folder.
2. Visit The XLab FAQs and read the FAQ on freeing up space on your hard drive.
3. Also, see Freeing space on your Mac OS X startup disk.
4. What is 'Other' and 'Purgeable' in About This Mac?
5. Files That Make Up the 'Other' Storage Category, and How to Remove Them
6. Free up storage space on your Mac.
7. See Where did my Disk Space go?.
8. Be sure to Empty the Trash to recover the space.
9. Replace the drive with a larger one. Check out OWC for drives, tutorials, and toolkits.
10. Use OmniDiskSweeper or GrandPerspective to search your drive for large files and where they are located.