We have a house that we built and we decked the kitchen side and put a tank on it. But recently water started dripping from the decking when it rained. What could be the possible solution to resolve this problem?

Clearly, the roofing has a leakage.

chatinent:
Clearly, the roofing has a leakage.

The roofing or the decking?

Get a good mason to rescreed the concrete deck top.

The mortar cement sand ratio should be ratio 1:3 and more importantly he should add waterproof chemical admixture to the mortar mixes.

Yes, "rescreeding" is one of the solutions.

"water de find its level". Meaning that the deck needs its top to be sloped outward so that the water flows out.

Another solution is felting. There're experts who provide said services here. You can consult them or go DIY. This solution doesn't eliminate the need to slope the top of the deck outward to discharge off accumulated rain water. Cheers