Do not sell your 135L & 85 F1.8.
Just buy the 85L II used. Use it for a month. If you find you can only keep one lens and the 85L is the one you want to keep for what you do, then sell the rest after you've really concluded that. But only sell your other lenses after you've spent time with the 85L. Not before. Don't sell stuff just to buy that lens. That you will likely regret. Do it the other way around. Buy first, sell after.
If you find the 85L isn't really what you thought it was going to be in every situation, then sell it. Virtually no loss. Just a deposit to rent it for a month or two basically. And put your 135L back on your camera and get back to it.
The 85L is a great lens for what it's good for, but it's not for everything. It's heavy, slow to focus, can miss focus depending on what camera you're using and what focus point, etc. You can get away with lower shutter speeds hand holding than with longer lenses, which is why 85's in general are really great. It gives you closer working room. It gets more light if you need it, but don't just park it at F1.2 and think that's all it does, it's still very special even at F1.4, F1.8 and F2 or even F2.8. Every time I see a photo with a headshot of someone with the 85L at F1.2 where the eyes are in focus, but the nose and other facial features are out of focus, I just sigh, as that's not a "good portrait" to me. But, to each their own.