Hi @valxander ,
Don’t know about a second RAM slot, but at 9:00 minutes into this [https://www.youtube.com/watch?v=UOuSVMyhUaQ&list=PLHWnjeX31Vwp2Ipo3LiuZyRk7uvIn2n2a|video] it is mentioned that there is 4GB of onboard RAM and that the total RAM can be increased to 12GB by inserting an appropriate 8GB RAM module into the slot.
You could verify this I suppose by turning on the laptop with the existing RAM module removed from the slot and check whether it starts or not and if it does how much RAM is being shown in BIOS or in the OS