You have to play the game the normal way until Naix hacks your server. After fixing your x-server.sys problem, you have to save the game and quit it.

Now copy your savegame in the folder C:\Users\USERNAME\Documents\My Games\Hacknet\Accounts.

Your savegame is named like save_myname.xml
That copy must be renamed to for example save_myname(naix revenge).xml

Back to the game you can send Naix some rude words to gain the achievement "RUDE"
Now you leave again and rename the copied savegame to the normal name again
So "save_myname(naix revenge).xml" becomes "save_myname.xml" again.

Now you can play further but this time you accept the Naix missions without insulting/offending him.
After Naix mission you can get to /EL/ Missions, and that will give you the second achievement " /el Sec Champion".

You can copy your savegames everytime, you want to repeat a mission or a special event in the game.
Just copy and move it to another direction or rename it.

Here you see a small picture of the savegame folder:

I hope you like my guide and sorry for my english.
I`m from germany. But I hope you were able to understand :-)
Greetz Horst