Complete all challenges/Missions/elusive Targets

Well its very simple.
Every time I could not go further I visited MrFreeze2244's channel.
Here's the Link to his channel:
https://www.youtube.com/channel/UC5S1IXqjZUf_PM2XhCM-4vg

He did a video to every challenge, to every Mission and every Elusive Target in HITMAN.

With his help I achieved a 100% completion of the game.

For you to watch how he is doing his videos: