Hello and welcome to the forum.
I see older threads with similar issues but the solutions offered are beyond my comprehension
That makes things difficult and it may be that you will need to seek professional help in resolving your problem, unless you have a more tech savvy friend, relative, neighbor or someone else in your social circle that you might be able to call on.
Some details as to "my PC" might be helpful....
Manufacturer Name, Model Name, Model Number
On the upside it apparently boots and what you refer to as a "screen saver" which I suspect is the lock screen cannot be dismissed by striking the space bar or by a mouse gesture would seem to indicate that neither of your two input devices are working.
My standard non-techie response would be to turn off the computer, disconnect it from AC power, if it is a laptop remove the battery.
In that condition, press and hold the power button for 30 seconds.
Remove any and all peripherals except.....
A USB wired keyboard
A USB wired mouse
A single monitor
NO other devices, no USB dongles for anything (wireless network, wireless keyboard, wireless mouse), no printers, no Ethernet connection, nothing but the bare minimum basics.
IF it's a laptop, replace the battery, reconnect the AC power and power it up and leave it alone for a while.
IF it is equipped with a hard disk activity light, keep an eye on that, if it appears to be on constantly or flashing rapidly, let it sit until it becomes less active.
Depending on the computer's horsepower and what is happening in the background it may take some time to stabilize and become responsive.
Failing that
It's likely going to require some hands on by someone who is.
I could suggest downloading the ISO, preparing installation media, booting from that and using the Windows Recovery Environment to troubleshoot, but.....
I have no idea whether any of that is within your skill set.