i have a 4 month old old english mastiff pup who is lovely and very well behaved overall but i could do with a bit of help with a few things, i cannot get him to go up or down the stairs, i cannot get him to walk on the lead and lastly and maybe most important he is a very freindly and plassid dog but today 2 friends came round and my dog became very nervous of them ,going to the top part of the living room, within about 10 minutes he came to sit with the rest of us but started to growl at the visitors for no reason, which is worrying for us giving that he will grow into a very big dog and we really need him to be very freindly with ppl. he never bites or growls at me my wife or kids.