What is the problem with using an 8 channel relay?

Hi!

I'm using an 8 channel relay module with my Arduino UNO but I also using I2C LCD screen so if all the relays are on the lcd backlight is low, I don't know much about electronics but I think the relays using to much power(?) How to solve that?

How to solve that?

Use an external power source able to deliver the required current rather than the 5V pin on the Arduino which is what I expect you are doing now

Thanks now with external power it's working good.