Definitely a greenhouse plant--or a houseplant, if you have a lot of light--in the winter. I would continue to feed it, but only at 1/4 strength, just to keep the plant healthy over the winter. It can go out in the summer, once frost is over. Judging by the sizes of plant and pot, I wouldn't expect flowering and fruiting until 2018. To continue the fruiting, don't transplant into a pot more than 10 cm larger than the previous one.

Each time you move it, the tree will go through "transplant shock" which will stunt the growth. Try to give it a permanent location where it can acclimate and thrive.

I would say the secret in growing these citrus plants is finding a suitable indoor position. Possibly sunny but not in direct sunlight, away from draughts, warm but not near radiators. Once you find a good spot then leave it there. The scent from the flowers is super but in my experience one of the most difficult plants to grow. They can suffer from mildew and keep a close eye out for red spider mite and scale insect. Sorry if I'm not too enthusiastic.

If I may add to Jimmytheone's answer, don't keep it TOO warm. It shouldn't be in heated surroundings, just make sure the temperature stays a couple of degrees above freezing. Don't overwater and make sure drainage is good. Light is key to survival.

Welcome back Gattina. Hope you are well and still thriving and gardening in Northern Italy.

Hi, Jimmy. Fancy you remembering me. Yes, still here, a little older, a little slower, but still here up in the beautiful sunny mountains, waiting for the first snowfall (some time on Thursday) with a cellar full of firewood, pasta, pelargoniums, cannas, long-life milk, wine, cats and snow shovels(to dig out the cabbages, sprouts, broccoli and leeks). We still have roses and cyclamen in flower, but they won't last long. Counting the days until spring and ordering seeds on-line.