I want a garden deck - don't know how to "start" this project! Help with basics please!

[Goodenoughisgoodenough]

Hi! Please be gentle, I'm clueless about diy/domestic/gardening stuff. I want to build a deck at the end of our garden it will be 3.5m x 3.5m. It won't be attached to our house or any building.The ground slopes, so it we'll be ground level at one edge with a drop of around 40cm at the other edge. Some questions:

How much will roughly would it cost for a landscaper to build this for us? (We're not in London).
How long would it take?
What about doing it ourselves? Me and DH. We're not very DIY at all. But have the time and energy. How "big" a project would it be for two amateurs?
Thank you 😊

Wooden decking gets slippery and doesn't last all that well and often provides a lovely home for rats to nest under.
I would say it would be easier to diy build a retaining wall with gabions and put a patio on the top but i guess it depends on how big the slope is?

What about doing it ourselves? Me and DH. We're not very DIY at all. But have the time and energy. How "big" a project would it be for two amateurs?
I would say:
The main thing is to make sure that the decking is strong and stable, not an accident-waiting-to-happen
Look on YouTube for examples e.g. Wickes has some. Also look at TV makeover programmes e.g. Garden Rescue. I've never laid decking either but it seems to me that as long as you have a spirit level and the power-tools then you are away ...
Useful rules: "the devil is in the detail" (3D corners!) and "measure twice, cut once".
I think the garden would be an excellent place to have a go. Practise your DIY skills there rather than in the house where the results are more visible!

Go for it!

(I agree with Geneticsbunny's post btw, but you have to start your DIY journey somewhere, and woodwork is easier and cheaper than masonrywork)