Question Adding another RAM

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Hi!
I currently have a GSKILL AEGIS 3000Mhz 8GB.
i have:
i3 9100f and gtx 1650S OC 4GB with a 500gb evo 860.
do i need to add another 8GB gskill aegis ram probably?
if yes please help with this:
my current ram is at 2400mhz( because of cpu limit)
but if i add a new(same as other) ram it will be at default (2133) that means i will have two rams one at 2400mhz and one at 2133mhz, won't it make a problem?

 

[rgd1101]

mixing ram that not in 1 kit sometime work. sometime don't