It may sound easy to get Companionship EXP from common sources, but it's not that easy to reach the maximum Friendship level on a character. Usually, it will take you around one month or one month and a half to reach the maximum Friendship level on a character. Depending on your availability to play the game, you may take less time, but usually, it's not possible to do all the tasks in one day or find the random events at places. There have been some players who have completed the progression in relatively less time but trust me, they really spend most of their time playing Genshin. Frankly speaking, I would recommend you to take things slow and invest in your characters at the same time. There have been times when I felt burnt out after playing for long hours and it's better to take a rest sometimes.