how long to harvest

Do a search on growing both potatoes and tomatoes and you will get heaps of advice on growing. As to harvesting lift potatoes, after checking, once they have flowered. Tomatoes will make it very obvious when they are ready to pick :-)

When you plant your tomatoes, make sure you plant them deep. Cover the stem up to at least the first set of true leaves possibly even the second. Make sure they get plenty of water. Pick off any suckers that sprout from between where the leaf meets the stem as the plant grows.