Welcome to the forum my fellow Warrington Neighbour
Max will be fine but you will have to introduce them slowly and carefully
When you first bring the older dog and the new dog/puppy to meet each other it is best to do this on neutral ground, such as at a neighbour's garden or a public place, but not one the older dog frequently walks with you. The older dog will be territorial about it's home and will view the new arrival as an intruder, rather than a new pack member.
Introduce the new puppy or dog into the family home gradually without initially intruding into the older dog's territory. If the older dog sleeps in the kitchen, try to keep the new dog in another room. Try and avoid allowing the new arrival into your bedroom or on the furniture if your older dog is not allowed access to these areas.
Stair gates are a great help in separating the two dogs during the settling in time. They can still sniff each other and get used to each other without getting too close and provides clear boundaries and space. A dog cage will give your new dog or puppy a safe retreat away from the older dog if you'd rather not use stair gates. Dog cages have the advantage of being easy to erect and are portable.
Give your older dog plenty of attention and try and maintain your normal routine as much as possible. that way it won't feel neglected or pushed out and will accept the new arrival more readily.
Gradually introduce the new arrival into the older dog's routine and activities.
Good Luck
From another Jo