How can I get information about bus lines between towns within Poland?

In the country I'm from (Switzerland), the standard way to travel between towns is by train, which is effective and fast. However, from my understanding, it seems that in Poland, aside with a few rare exceptions (such as Warsaw-Kraków), there are no fast train lines which stop only at large towns, only regional trains which stops at every station, which means travelling in Poland by train is awfully slow.

On my last visit, we were lucky as we caught a bus line by pure chance which allowed us to go from Kraków to Katowice in only 1:30, instead of almost 3 hours. Apparently bus is the standard way of long-distance travel in Poland, instead of trains like it is in Switzerland. Also, every town has it's Dworzec Autobusowy, which is something like a huge bus station (something that doesn't exist in my country).

How can I get information about what bus lines exists, where they stop, travel time, etc... before actually going to Poland? It seems the situation is complicated as there are multiple bus companies and each one only provides timetables for their own buses.

Is there a centralized website about timetables from all bus companies, and possibly trains as well, so we can have an idea how to efficiently travel from point A to point B using public transportation in Poland?

EDIT : The website e-podroznik.pl mentioned in one answer can show connexions between various places in Poland and by various companies. That looks great on first sight, however it requires you to specify a travel date, and in order to find about for example weekly connexions you have no other choice but try all days of the week one after another. The second annoyance is that it only says the destination and stops of the suggested connexion from point A to point B. It does not show the whole bus or train lines, nor can you easily see various daily connexion of the same line.

If you're lucky you can have such time tables by looking at the website of the train or bus company, but unfortunately, some buses suggested by e-podroznik seems that they either don't exist or they are not shown at all on the website of the company. In particular, I was looking for buses between Prudnik and Opole. While e-podroznik suggest a line of the company Arriva, their very own website does not show any mention of a bus line in this region.

Even worse, searching on their website simply redirects to back to e-podroznik... with the same issues.

Now what's even worse if I go to Google Maps in that area, there seems to be no mention of that Arriva bus line, but there seems to be another bus line by another company... which is not found by e-pozdernik. Since neither e-pozdernik nor Google are transport companies, their info cannot be considered accurate.

So considering all this stuff, I am not looking for extremely-cheap Flixbus-style crap, I am looking for normal public transportations where you can go to the stop, buy your ticket and, well, get transported. Is there any way to have online information about such a network in advance ?

Ideally I'd be looking for something like this but in Poland. I know such a thing might not exist, but I'd want something as close as possible : Showing all connexions for all lines (train and buses) for a year - not just something trying to sell you a ticket without giving you any information about the lines themselves.