You could certainly use 'I'm hiding', because that's what you're doing at the time of writing ie 'now'. 'Have been hiding' tells us that you've been doing this for a while, presumably since you came back from the bank, but either form is fine here. A few other points about your text: 'was all around my city' doesn't sound quite right. Why 'all around'? Maybe 'went all around' would be better, if you went to many places, or just 'was in my city' ? 'dark area' seems strange. Perhaps 'shady area because the weather was hot'? 'after I'd finished studying' would be better. 'I want to go to the seaside' (article needed) and the second half of that sentence with 'because' doesn't seem logical. Surely you want to go to the seaside because it's hot, not because you can't go? Otherwise all good! Not so hot where I am today, so it's nice to know that it's summer somewhere in Europe.

it is correct to say I AM HIDING, because 'I have been hiding' means 'for a certain time till now', and there is no such meaning in your text.