so the cheapest ddr4 8gb ram at the time i built my pc was $100 + free shipping

im using a 2400g and vega 11 the ram speed is 2400mhz

the price of ddr4 ram has come down in price a lot now i see so i think its time to upgrade

i can get another 8gb of ram the same that is in my pc now $50.90 that includes shipping but the speed is 2666mhz

the speed of the new ram stick is faster will it matter? i heard somewhere or from somebody i could set the other ram to 2666mhz but i am scared to as i might break the ram