Hi there and Welcome to the forum!
Lots of good information here passed around and lots of beautiful dogs you’ll see.
Be sure to take lots of photos of your puppy as everyone here loves photos!
Feel free to look at my post , I have an OEM myself and he turns 4 months old on the 22nd and already weighs 77lbs!
As far as nutrition goes you’ll get mixed opinions saying keep protein low, for slower more optimal growth. Then others that say high protein for maximum muscle development. After tons of research I decided on my EM to go high protein. Low fat.
With these dogs they do tent to bloat and also tent to be overweight. You want low fat content and under no circumstance any soy bean. The food I decided on overall is Acana Large Breed Adult. It’s the perfect formula that promotes growth, muscle development along with healthy hips and joints. My little guy being nearly 4 months old eats 10 cups a day of that. About 4000 calories a day. So be prepared to spend the big money on food. I spend $210 a month Canadian on food for my guy.
Training wise you have to be extremely laid back because these dogs are on Mastiff time. They don’t do anything in a hurry. The best way I found my guy to learn was by treats obviously. He loves his freeze dried liver. I let him smell it , so he knows what he’s getting. Then I give him his command. To initially teach it. I would let him smell the treat. Make him sit, lay down, etc. Then give it to him and say good boy! He learnt that was what I wanted him to do. So he did it when I told him to. They’re very stubborn but listen well with food. Even now when he’s outside playing and I tell him inside he won’t always go. But I show him the treat and say inside, he’s going!
These dogs sleep a lot. Eat a lot. And poop a lot. They don’t need much exercise at all. Don’t run them at all and no long walks till they’re over 2 years of age as their growth plates don’t close till then. Avoid letting your pup jump as well. Not off the bed. Out of the vehicle. Always assist them getting down or getting up as their joints are growing so much. My pup gains over a pound a day in weight. I can only imagine what his body is going through.
hope that helps! Anything else feel free to ask. I’m sure others will chime in