Exactly, politicians are payed to make decisions.

no sorry. it is not a job. they aren't shepards guiding the lost flocks. It is isn't because you renounced your pursuit of liberty and happyness for the comfort of being ruled and owned that you can impose your way on others.

1. politicians get compensated to make laws or apply laws. this is the distinction between congress (legislative) and trump (executive).

2. which kind of decision? this is the core of the question. The usa is a REPUBLIC as such they can't decide on certain aspects. Otherwise they have to succeed in dismantling the republic. Do you want your toilet usage regulated? for your own good or for the common interest it has been decided that @jocchen can only go to the toilet once every 2 days under threat of duress by any violation.

I don't want to say there is no chance for corruption and / or other crimes,

you just did. it is called centralization vs decentralization. Is it easier to corrupt the top or the bottom of an organization? It depends. In the case of the usa we can see that bill clinton raped us citizens impunitly and hillary crimes are still unpunished. You can use the framework of what happen to the female us olympic team members to understand better the situation. If those girls could have had a voice and veto or vote their staffs I don't see how it could have happened.

but to start a referendum for all and everything makes the system much more sluggish or even stops processes at all.

I think you don't understand the difficulty to organize a votation. those votes are exactly designed to address problems without having politicians or judges decide (representative) but the people affected. for example do the people in this town want to make it a dry town? this will affect them, and the minority will be subjugated to the determined will of the majority on THIS ISSUE ONLY. because when it comes to the swimmingpool the political line shift and again for the next issue. So it makes only the system sluggish or even halt in direction where a significant part of the population isn't happy. And the great thing is that when politicans do a proposal that no one is against they know that they decided well.

There are good reasons to do referendums in special cases, but I still think it should not be the standard for many small decisions.

what is a small decisions? a swimming pool? a drytown? banning raw milk interstate trading? I ask... or maybe it is abortion? you see.

I also claim that often after some time 50% of the voters are not happy with the decision,

vote again! who cares if what ever happens as long as it is not the destruction of the country... think about the civil war... is it better to have a lack of decision on a certain issue or a civil war? remember this is the cost of peace.

but complain about bad or incomplete upfront information or they were just not able to see mid and long term effects.

who cares vote again, they will learn.

So the bad guys are no longer the decision maker, which is wonderful for politicians, but other institution like press, populists etc. or just your neighbor.

do you want your neighbor to prepare for civil war?