I am pretty sure our pooch has a bit of pit bull in her, for sure. Her bottom lip has the pittie wrinkles to it. I figure that and some hound/beagle. She's darn smart, that's for sure.Saylor will not be "full grown" as far as Newfoundlands go, because they do not reach full maturity until they are between 2 to 3 yrs old. Currently, Saylor (landseer newfie) in the background of that pic weights in @ 112 lbs.@ 1.5 yrs old. The breeder we got both dogs from told us that Libby will be bigger than Saylor, and you can compare the size and feet of your dog compared to Libby's.
Your pup may possibly be a mix of Great Dane/Pitbull and something else. Puppies with big feet and legs grow to be big dogs!