Improving my soil

The soil in those raised beds looks very dry and compacted and that always makes it harder to work. Adding organic matter as descrived by posters above will help with that. You'll need to do it every autumn once there's been some good rain, or water the beds first, and then let the worms, micro-organisms and weather work it in. After that a light forking by hand will loosen it up for planting.

What @fairygirl says about your lining being too low is true too but, rather than try and remedy that by emptying and relining you could brush a protective oil over the exposed wood to improve its water resistance. Teak oil is good, or Danish oil, but also ordinary olive for cooking - not extra virigin - mixed with the juice of a lemon per litre will do very well too.

 

That would certainly be a solution @Obelix-Vendée [the oil on the timber] but the problem of the planting still remains. You can't top the beds up properly unless the plants in there are annuals, and will be getting cut down so it won't matter if anything's added. If the planting's perennial, and permanent, that amount of material will likely see them off, so they'd have to be dug up temporarily, then replanted - weather permitting, or possibly in spring when the level settles.

Leaving the soil level so low isn't ideal, but if the soil is also not very manageable for you @LindaB, that makes it hard to alter planting in any way, even if the aesthetics are acceptable. I wonder if they've been filled with turf, as that doesn't always break down quickly, and isn't great if you're trying to plant into it. It has that look about it, especially as you mentioned only a small layer of workable soil at the top?
Many plants are happy once established, so it wouldn't be a problem for them to grow there, but it is a problem for you if you want to make changes.

 

It looks to me @fairygirl and @LindaB as tho the beds are empty so topping up the soil with organic matter won't be a problem.

If not, then any plants remaining need to be lifted first. If they're perennials or shrubs then they need a good watering, left to soak it up for an hour or so and then lifting out while the beds are topped up then put back as soon as possible and watered again. Best done in autumn when most plants are going formant for winter.

 

I wasn't sure if the plants had all been removed @Obelix-Vendée and all beds were empty, or if some of the pix were different, empty beds, and not that first one! If the plants aren't there, then it's easy.
I like to leave any additional material to settle, then add more before planting, but it all depends on the plants, and what's going back in or not.
If small plants are going in, I'd leave those to grow on until next year, as I wouldn't plant out anything small here in late autumn/early winter, but it always depends on the type of plant, and the location/climate etc. Anything woody/shrubby of a decent size or a very hardy type would be fine, especially if it was something home produced and used to the conditions.