The first RAM you linked to is for a desktop system not a laptop so it is not compatible. Crucial does make the most Dell compatible RAM and they have European sites to order from such as here. And yes an SSD would improve performance and they are not difficult to install and setup.
Hi I have a Dell g3 15 3579 laptop, specs are i7 8th gen,  GTX 1060, 8gb RAM and I want to upgrade the RAM but I'm getting a bit confused over what is compatible and what isn't for my laptop (I found ones that should be ok for similar but don't know if they are also compatible with my configuration).I found this one which I think is the same as one that I found on crucial that said it was compatible (had to look separately with the name because it only linked to american sites and I'm in the UK) but I'm not sure. Also was wondering if it was worth trying to swap to SSD as the Crucial website also listed compatible SSD but I'm not sure if that would be more complicated/difficult, I'm sure it would likely cost more and I don't know if it's worth the extra effort/money. I primarily use my laptop for gaming but I'm running out of space.   Thanks in advance and sorry I don't really know what I'm doing 
Dell g3 series 15 3579 RAM Upgrade