Is it possible to connect to multiple WLANs with different ISPs
to gain a super fast internet connection?

I see the problem with this would be if computer1 is sending
data to computer2, but computer2 unexpectedly receive the ACK
from another IP address due to the multiple WLANs that computer1
is getting its internet connection from.

A solution to this problem could be to make the packets to
travel through the same network interface so the same IP would
send all the information from the same internet address.

This is what the setup could look like
________
|(192.168.0.2)-----WLAN1-----ISP1(80.33.42.103)
Router |(192.168.0.156)---WLAN2-----ISP2(217.209.134.24)
________|(192.168.0.2)-----WLAN3-----ISP3(12.61.30.98)
eth0
|
|
|
eth0
------------
Workstation|
------------

I don't know very much about this topic, but I would very much like
to hear from the rest of you what you think about this, or know
if anything like this already exists.

Are you saying that you have a single router that has three WAN connections to different ISP's ... and you want all three WAN connections to be bonded to appear as one interface so your bandwidth is triple ??

The answer is no.

There could be a possibility if all three WAN connections went to the same ISP AND they have provided you with multi-chassis MLPPP ... which is doubtful as they would normally offer another service with higher bandwith at a larger price.

Ok, thanks for letting me know. I will study the problem further to see if there is any onther solution I can come up with.