It's really great to see your passion for gardening! Since you are interested in mangoes, I have a small piece of advice for you. Growing mangoes from seeds (stones) takes a lot of time to bear fruit. Instead, you should try buying a grafted mango sapling (কলম চারা). Grafted trees are often small in size but can produce a lot of mangoes within just a year of planting.
​The best part is, since you have space constraints, you can easily plant a grafted tree in a large bucket or a drum with soil and keep it on your balcony or rooftop. It works perfectly! Keep up the good work, and I hope to see you harvesting your own mangoes soon!