If these are annuals, use a multi-purpose compost with added water retaining granules if you can get them - and feed them every week with a diluted tomato feed. If they are perennials, much the same, but a John Innes compost would probably be better for them. You'll still need to feed them, less often though.

Watering - possibly twice a day in hot weather!

Don't try growing potted plants in pure sand though!

Wonder if they have bagged compost in Bangladesh? I've no idea what your soil will be like Guest but if it is reasonably open and free draining it should be okay. If not try to add some grit and some garden compost.

Do join GoY so we can help you better.

No idea whether this guest can buy bags of compost, Mg - but we can do nothing but answer from our own experience, can we?

I doubt anything we suggest is going to help Barbara