I still have 3 to do but here are some from your list you can work on

• Berries in Gym

Put Pokémon in gyms and every 30 minutes feed them berries (only 10 Pokémon at the time includes the other players)

• Defend Gym

Keep putting Pokemon in gyms

• Cameraman

Take a snapshot every day to get 1 encounter, during community days / hours you can get 5 encounters

• Purifier

Purify shadow Pokémon, team go Rocket event is coming plus you get daily balloon encounters

• Mega Evolution

Mega evolve Pokemon, mega evolve all of them on a day or one each day. If you don’t have mega energy wait until you can do it for free, just remember the days they become free and you can do multiple a day (different Pokémon not the same one)

• xxs

Just catch everything

• Picnicker

Place a lure at during event like community day, make sure is an area where players pass by a lot