First mac any help appreciated

Hi everyone. I got my first mac. I downloaded a third party app. The app asked me to download an install helper and then to "enable permission" I had to enter my password under security section of Mac when I enabled. After I restarted my mac it was acting all weird. I was able to go to the login screen but when I entered my password the screen would go pink for a second then grey. There was a pop saying error can ignore it or send to apple but when I try to click or move my Moshe everything was frozen (even wired external mouse). I tried the following: -enter mac with safe mode (would not let me enter safe mode) -reset SMC -enter recovery and try to erase drive (would not let me erase drive) -try to reinstall OS through wifi and would not let me install with pop saying that I need an active internet connection (internet working on every other device) -eventually I was able to enter the reinstall OS by using an Ethernet cable. It's downloading OSX right now so I'm hoping it will install it. I just wanted to know if anyone has ebocuntered this virus or malware before? How can I ensure once the OSX installs that someone won't have access to my computer or any of my info? I also should mention the enter key wasn't working I had to use the space key which was so weird. like someone purposely designed this to make it hard to enter my avvount, recovery or enable recovery. I am sorry for the novice question I'm hoping the reinstall fixes everything but was wondering if anyone came across this before