What options aomebody has as a (long-term renter, owner) to get fast internet in his condo? How fast or slow the in-house WiFi usually ?

Which condo; everyone is different.

Ask at the management what is available.

Different buildings, different ISPs, different types of service.

And even if your neighbor has it doesn't mean the ISP has the capacity to provide the same service to you.

You can usually arrange your own internet connection into a condo, you will be restricted to whatever company has run cables into the condo block basement/risers, and you will usually be restricted to A/VDSL (50mbps) using phone cable.

In house wifi can be expensive as charged at a daily or weekly rate, and speed would depend on how many users etc.

As an alternative you can get a sim with decent speed, use phone, or wireless router. depends what you use internet for, usage and speeds required. I use AIS and DTAC sims in the condo

As pointed out by others, ask the management which providers (AIS, True, 3BB...) are available (may be just one), then contact the provider and ask what they offer (some condos have only phone lines, then you can only get 50mbps vdsl, if your condo has fiber you have all the options, the provider will know what's possible)