Could you recommend exercises for someone with 'an increased valgus alignment of the calcaneus' of the right leg. how would one improve this?

Custom Orthotics: A proper custom orthotic is your best bet.

You Mean A Flat Foot: This is usually treated with custom shoe inserts ("orthotics") that lift and support the arch. Try some from a local store like Rite-Aid or Walgreens. That might be enough. I've been told that walking in dry sand at the beach helps a little. I've also heard of putting a towel on the floor and grabbing or rolling it up with the toes, but I don't know if any of that helps.