What should be the watts of solar panel and battery size
70 W * 12 hours = 840 Wh. That is how much energy you need to take out of the battery every night and put back in every day. If you want the battery to last, you should pick a battery with twice that capacity. So that is around 1700 Wh. 1700 Wh / 12 V = around 142 Ah at 12V. Pretty big battery. You cannot discharge a battery 100% every day. It will not last long.

The solar panel needs to produce 840 Wh in about 5 hours. So that is 840 / 5 = 168 Watts. This is just a rule of thumb. The daily output of a solar panel is around 5 hours * rated power. Obviously there is some variation depending on location and season. You might want to look into data specific to your location.

So there you go. A 12V 142 Ah battery. A 168W solar panel. And a good solar charge controller with maximum power point tracking (MPPT).