The most popular free antivirus program among ABers seems to be Avast:
https://www.avast.com/en-gb/index
(It's what I use)
That should be topped up with an anti-malware program. The most popular freebie, by far, is Malwarebytes:
https://www.malwarebytes.com/
(They keep changing the way it installs. At one time you could look for an option, during the installation process, to deselect the offer of a free trial of the paid-for 'Premium' version. Then they changed it to force you to take the trial anyway. It now looks as if they might have gone back to the old way of doing things. You should avoid the trial if possible but don't worry if you end up accepting it; the program reverts to the free version after 14 days anyway).
The free version of Malwarebytes is 'run on demand' only. So it will do absolutely nothing unless you remember to run it occasionally. (I suggest once per fortnight, plus immediately after installing any new software and whenever you suspect that there might be some malware on your computer).
Whenever you install free software (such as that pdf converter you've got) you need to check very carefully that you're not accepting unwanted stuff by default. If you see a 'Custom installation' option you should always accept it, as that's often the only way to avoid geting things like the MyWay browser hijacker you've now got.
Fortunately, simply running Malwarebytes will probably get rid of MyWay but you might need to restore your web browser to its default settings (or, at least, look for an unwanted extension) if that doesn't work. Tell us which browser you're using if you need help with that.