Inspiron 15 5555 locked in Safe Mode

 I have a Dell Inspiron 5555 I bought a couple years ago. It's been slow as molasses ever since I bought it ; as a result I've used it like 6 times.

Trying to speed it up, I was following some tips on the internet that required it to be put into Safe Mode . What they do NOT tell anyone is the 4 digit pin I use to get into Windows 10 does not work in Safe Mode and instead I must use some password string. I've never used any passwords to get into this thing so I have no idea what it is at all. This laptop did not come with a Windows 10 disk or any type of rescue disk. 

I was going to try to get to a command prompt at boot time by holding the Shift key while clicking RESTART. That got me to the TROUBLESHOOT screen, then Advanced Options, but it even wants a Safe Mode pwd to open the command prompt! How do I get around this and get this #$DS@! thing out of Safe Mode?