Yep... more exercise. Physical and mental, both, will help.
It sounds a little like a cry for attention, too... he wants you to play with him, and he's learning what works to get your attention (good or bad)... if climbing on the couch means you grab the leash and go for a walk, you can bet he'll be doing that more often!
That's the trouble with smart puppies... they learn your buttons and push them... often...
We have a "no zoomies in the house" rule - so if those start up inside, a quick "OUTSIDE" for zipping around helps to burn the energy and get it out of the puppy's system (a fenced in yard is a must in that case). Adding in an extra walk, some flirt-pole time and/or a visit to a new & exciting place (or just the outdoor mall) for some socialization is then added to the next day's activities, for some extra-energy burn-off activity.
Puppies and dogs (and human kids) also like structure... it removes some of the 'unknown', which can be frustrating or scary... so consistent rules with firm, confident, and benevolent enforcement can go a long way to shaping the puppy's behavior, too. I agree with Tosa, too... be sure you out-stubborn your mastiff! Only give in today what you're willing to give up tomorrow, too...
For the couch issue - work on "place" - and be sure you randomly reward the puppy being on his bed/place - even when you didn't ask him to be there. Make him start to anticipate what you want (using that smart brain of his) - in order to maybe get a treat, or a pat on the head, or just a 'good boy'.... instead of needing to get the "NO! OFF!" attention that he's currently getting - just so he can have some interaction time with you.
As for "a phase"... sure - we all have 'phases'.... if we have extra energy to burn, our phase will be to test the limits, and get crazy... if we've had a great day hiking all over a mountain, our phase will be to curl up in front of the fire for some cuddle time.... diet, exercise, hormones, sunshine, moon-phase... anything and everything can change the 'phase' we're in (I'm talking about me, too)... so, consistency across all phases is important. As is recognizing the source of unwanted behavior - like you said, a need for more exercise is often the culprit.