I bought it a month ago then moved it to a bigger pot and the tomato started to be red but still too small, it is cherry tomato but still too small and not tasty sweet at all.
Tomatoes, and most soft fruits, need good sunlight to sweeten up as they ripen. If you're growing indoors, whilst they will ripen, they won't be as tasty and sweet as they would if grown outdoors in warm/hot sunlight. This is why tomatoes harvested in summer are sweeter than those grown in greenhouses under artificial light/heat conditions in winter - the latter are certainly edible, but not so tasty. if your plant is not a small tomato like a cherry variety, they haven't reached full size because they're being grown indoors under ordinary house conditions, though lack of tomato fertiliser on a regular basis may also partially account for it - you haven't said what your care routine is.