Do you mean lag happening in C&C Rivals?
You can try to compare the following:
1.) Play over mobile data
2.) Play over a Wifi router
3.) Play with a direct cable connection to the Internet. For this, you need an emulator like BlueStacks running on a PC or a Mac.
If option 1. and 3. give you a good performance (very little to no lag), but 2. does not, then chances are that your Wifi router is crap. Rivals unfortunately needs a very good Wifi router with very low latency, not every model is capable of providing that.