From my understanding, this means that at 2028,after the halving the increase in supply will reduce to 1.5625 and at 2032, it will halve 0.178 and so on..
0.78125 BTC, rather than 0.178 BTC, but essentially you are correct. The dates are not set in stone, however. A halving occurs every 210,000 blocks, which on average will be almost 4 years, but not necessarily so.
If at 2140 the amount of bitcoin mined reduces,at what year do you think miners will not have any fraction of bitcoin to mine ? Or will they depend on transaction fee to keep the mining business ongoing ?
After the final halving in approximately 2140, the block subsidy will be zero, and all the reward that miners receive for mining will come from transaction fees. It will be several decades before this however that the block subsidy becomes so small as to be insignificant when compared to fees.
Don't you think that this will affect the price of bitcoin and its availability for a poor man to purchase. This means that at the long run bitcoin will not be able to be adopted by everyone due to very little supply.
I don't think so. If it becomes too expensive to own a single bitcoin, then buy a millibitcoin. If that becomes too expensive, then buy a few thousand sats.