As you can see above, hashrate is decreasing
that chart is completely wrong. we have no method of measuring hashrate in such a small time frame. they are basically taking the time between blocks and use that to compute hashrate which is wrong because block hashes are completely random, miners could get lucky and find them faster or unlucky and find them slower (eg. 1-2 seconds between blocks versus 1 hour between them). that doesn't mean hashrate has gone up or down in matter of days.
the only correct (closer to be correct but still not accurate) value for hashrat is when it is measured over a longer time such as the difficulty adjustment period which is 2 weeks.
after the halving as expected.
wrong, you can not expect what will happen to the hashrate just because of halving.
Due to that, the fee has increased
wrong. fees only rise when there is a surge in number of transactions. considering the fact that price has been fluctuation hard and it has gone up nearly 15% it is understandable to see an increased number of transactions hence an increased amount of fee.
and according to bitcoinfees, the recommded fee is 150 sat / per byte
that site is the worst place to check the fees, it is always
overestimating fees
on purpose. right now as they suggest 150 as "The fastest and cheapest transaction fee" the reality is that around 100 to 110 gives you the fastest and cheapest fee. in other words they are reporting 50% higher fees!
After halving, we can say some miners have left. What do you think? More miners will leave too? And what if hashrate drop more?
no you can't say that, although i think naturally some miners did leave but we still have no evidence to support that. at least another week has to pass for us to be able to make that conclusion.