I would like to know if I can easily join an airline with an fATPL at about age of 23 - 25.
Who knows? If there's a boom and there's a shortage? What you MUST remember, is that jobs for low houred inexperience pilots are always hard to find. Do not believe the sales pitch.
If you can't do the full monty full time uber expensive course, then look at CTC Wings. Not that I recommend giving them any money what so ever, but that may be an option.