Squirtle event is over but still have 2 quest left

If you see enough Squirtles while playing the game normally, you can. The relevant question is how long will it take you to fulfill them, and what quests will you not be able to do while you fulfill these.

Do you know if there's a Squirtle nest in your area? I'd ask your local Facebook/Discord/whatever group if there is and knock them both out.

Do you KNOW if one of them came from a stop that gave out guaranteed shiny sunglasses squirtle? If so, you might keep them.

Just discard them if you can't find more Squirtles.

Try to get one of the research tasks that result in a possible Squirtle encounter. To my knowledge there are three at the moment, unfortunately none that definitely results in a Squirtle:
- win 1 gym fight (Squirtle, Bulbasaur, Charmander)
- power-up 5 pokémon (Squirtle, Bulbasaur, Charmander)
- evolve 1 water pokémon (Squirtle, Seel)