I'm not so keen on the Duna Fun large myself. It is also very expensive for what it is. It is basically a standard duna multy but a bit taller due to the extra bar section between the plastic base and top. I have seen issues with the gap between the ladders and platforms on some cages like this too, but it may have been a similar one and not the Ferplast one (ie hamster getting a cut or foot caught in the gap where the solid ladder meets the solid platform. But that kind of thing can be sorted/adjusted to make it safe.
For a dwarf hamster it is quite tall (ie fall risks) and more issues with gaps between ladders and shelves with their small feet. But if set up carefully that can be avoided.
Having said that, it's not a bad cage overall! But there are better cheaper options, especially for a dwarf hamster.
Is it this one you mean?
Cage Duna Large Fun
This is the same cage without the barred section and about half the price (standard duna multy) -comes in red or blue as well.
Cage Duna Multy
If you like the idea of a cage with extra levels, then Zooplus has a good range of Hamster cages that are reasonably priced. The Hamster Heaven is popular. Also the Savic Mickey 2XL is a good cage for a dwarf hamster (same as Hamster Heaven but smaller bar spacing, but also a bit expensive).
Most people find it is better to have tubes as in cage toys rather than as linking tubes as hamsters have a tendency to block the tubes off with bedding and pee in them plus it's an escape route! Makes the cage a bit less secure.
Same goes for the hamster heaven - people often end up removing the tubes and penthouse and blocking off the tube holes. But it is a good basic cage with a lovely big front door for good access and easy interaction with a hamster, and a good size - not too big, not too small, and not too tall either.
On this page, the ones suitable for a dwarf hamster would be
Hamster Heaven
Alaska cage (possibly - would need setting up to avoid fall risks).
Barney cage (has 7mm bar spacing - same height considerations as Alaska)
Alexander cage (ditto)
Kerry Terrarium (similar size to the Duna fun large but better floor area and not so high)
Hamster Cages | great selection at zooplus
There are also these two on Amazon
Rivierra Varazze mouse cage - 6 to 7mm bar spacing
https://www.amazon.co.uk/Riviera-Var...s=riviera+cage
Grosvenor rat and hamster cage - low height
https://www.amazon.co.uk/Little-Frie...and+mouse+cage
This is the Savic Mickey 2XL - I love this cage - I found it not quite big enough for our large Syrian who has large stuff! But it's an excellent cage for a dwarf hamster or mouse. No tube holes to block off like the hamster heaven. It comes with a couple of in cage tubes as toys, a basic wheel, a sputnik, water bottle and food bowl. The metal grid shelf needs taking out - intended for mice and bad for hammy feet, but a flat roofed house can make a good shelf or you can buy a plastic or wood shelf quite cheaply.
The big downside is the price and it only seems to be available on Amazon. The biggest plus sides are the build quality (very sturdy well made cage), the narrow bar spacing, the flat roof on top for hanging things, and the huge front opening door and quite deep base for substrate.
https://www.amazon.co.uk/Savic-Micke...vic+Mickey+2XL
At the time I got this I thought it was worth paying a bit more for as suitable for any species of hamster, also fine for a Syrian as long as you don't have a giant one like ours!
As for being a bit shy and nervous - with an open style of cage you can create lots of hidey places at floor level easily with tubes, tunnels, cardboard boxes and other little hideouts, plus a good sized house with a flat roof makes a nice dark nesting box and doubles up as a shelf. Or just adding a shelf or platform to any cage can achieve the cover.
I find with "cover" such as levels - it's balance between having something to hide under and access underneath the shelves - a top opening access only would make it difficult to see/do things under the shelves or pick up the hamster maybe. Front opening access makes this easier. With the standard duna multy the top opening access is easier because it is lower and you can reach most of the cage easily inside.
But if you really like the Duna Fun large it's not a bad cage
Edit: Posted at the same time as Cypher