I would like to be President of my country and purify it from corruption. Even in one day you can make several decisions which can change the situation in the country for many years to come. It seems to me that presidents don't do it only because they care about their future. The smaller the period the less opportunity to make money by corruption and the more willing to pass laws that will help earn money honestly.
I think there's quite a few flaws with your idea of what a president can and / or should do.
I would like to be President of my country and purify it from corruption.
Unless you redesign the entire political system (which takes hundreds to thousands of years to actually get adopted and practiced) with a variant that solves all the current issues with modern democracy (the best we currently have) or the societal mindset changes immensely (as in each and every politician that gets elected, has an unbreakable respect for laws, stronger than the temptation of massive amounts of money; highly unlikely to happen within the next thousand years), completely eliminating corruption is, if not impossible, at least extremely temporary. Unless the system itself directly (rather than via fines, jail time, etc.) deincentivises corruption (via some still undiscovered method; e.g. not breaking the rules always nets you more both in the short and long term), it'll continue to happen as generally humans tend to take the path of least resistance while attempting to reach their goals (e.g. becoming prosperous).
Even in one day you can make several decisions which can change the situation in the country for many years to come.
Indeed, that's why politicians often spend days to sometimes years on end deciding on issues. Not only do you have to properly predict what your descision will impact for years if not decades to come but also have to do so in an enviroment where there might be 5 people criticising your descision for each one that agrees.
It seems to me that presidents don't do it only because they care about their future.
Yes, as, unlike dictators who can carve out their private paradise, they more or less will have to live within the society they affected during their term.
The smaller the period the less opportunity to make money by corruption and the more willing to pass laws that will help earn money honestly.
While it can't be denied that power, money and political pressure will and usually does affect descisions made by politicians, as they say "the road to hell is paved with good intentions". Without an extensive understanding of the current political, economic and societal landscape, good intentions can translate into horrendous laws that merely cause more trouble (see:
https://en.m.wikipedia.org/wiki/Prohibition_in_the_United_States).
Also, I'm not quite sure what sort of political system is in your country, but presidents, in most cases, don't really have that much power. They represent the nation to the outside world, handle diplomatic relations and merely attempt to push the rest of the government towards a direction they think is right. If you had a single day, you'd maybe make a single descision that'll either get reverted or denied the second you're out of office.
