can I continue to progress in the game and if so how?

There's a lot of wildlife you haven't attracted yet. Also quests you can do. Level 42 just means you have planted and harvested the required number of plants.

While you've reached level 42, you definitely have an amazing number of wildlife left to both spot (you've spotted just 33 of 573 of FL Critters and attracted 11 of 573) so you could work at coloring in your wildlife pics. You haven't completed any challenges or quests yet and there are lots of each to do.

  The hardest part might be narrowing down your choices to just one to start. It might be best to first take stock of your resources (blue and pink diamonds and amber and sunlight seeds) then focus on building those by spotting multiples of 10 of a critter. As you spot you'll start to accumulate resources that will help as you work on challenges or quests. If you leave a post as you visit, you'll have players visit you to spot critters in your garden.

I've never seen stats like that in a 15 year old garden. You'll be discovering a whole new - and enchanting  - aspect of the game.

Have fun!

Your next goal can be to reach Legendary status through amassing wildlife diamonds. Right now you are Highly Skilled. I think you unlock unicorns and mushrooms by progressing up. The mushrooms can help you in many setups.

At the completion of level 42 you can now attract the panda, gorilla and red panda. Those are bonus critters for having gotten to this level. Maybe that would be an idea to try? They give a nice amount of gems too when spotted...and would add to your gem total which in turn helps progress you to the next legendary level which might be your next goal(what Kelly mentioned above).

If you haven't attracted many birds yet, maybe try building nests? Because the first of every bird will help build the nest in your garden, after that it's every fifth. Might as well benefit twice from attracting once!