@Vytautem Adding another 8 GB RAM for 40€ would be an excellent investment overall, whether it helps Sims 4 a lot or a little. It would certainly help with multitasking, both while you're playing and not, because swapping data from RAM to the page file (where the overflow data goes when it doesn't fit in RAM) is much slower than leaving everything in RAM.
Additionally, if your laptop does NOT have a dedicated graphics card, and I don't know whether it does based only on the model, 8 GB is only barely sufficient for Sims 4. An integrated graphics chip borrows from RAM to do its graphics processing, as opposed to a dedicated card that has its own memory. So that 8 GB installed RAM can become 6 GB very quickly, with 2-3 GB taken by Windows as well.
Regardless, if this is a cheap and feasible upgrade for you, it's absolutely a great idea and will make the laptop run better and for longer.