There’s special plasticized concrete in caulk tubes. I liked one brand a lot better than the other, but I can’t recall which one was better.
Power wash the cracks first.
Check out Sika. I've not used it but saw an amazing demo.
I filled the cracks on my patio with dry cement and water. I used Quick Crete that will dry pretty quickly. I spread the dry, powdery Quick Crete over the area and then using the water hose sprayed it down. When it was dry the cracks were covered. If all of the cracks are not covered the first time, repeat the process. It will pay in the long run if you get the best paint specificly made for cement.
You need to re-create a mixture using cement and water but make sure it's more liquid than solid. When this is done then add the mixture in the cracks and use a sponge to clean the excess