I'm not familiar with that particular board (nice case though!), I assume it is a generic ESP32 (successor of the ESP8266) with a relatively generic OLED display?
I've been tinkering with an ESP8266 the past few weeks, and have to say that I love them. Fast, more memory, cheap, wifi build in. Nice!
Getting started was super easy as well. (see my article)
Since both GPS and SD card use digital pins, I'm confident they will work with the ESP32.
I guess selecting the right pins can be the confusing part - but all in all it does look very similar to the ESP8266.
This Stackoverflow post may be helpful.
With the ESP8266 I found it to have more digital pins, but fewer analog pins (not an issue for my projects, and I understand the ESP32 is better equipped than the ESP8266).
Personally, I'd go for one of the MakerFocus models (Amazon.com, I couldn't find it at Amazon.de, but I did find this alternative that looks exactly the same, and an ESP8266 alternative), but I'm biased haha.
My ESP8266 is from MakerFocus and I'm very pleased with it.
Funny, while looking at the ESP32 from Amazon.de, I did find this link that may be helpful (also Heltec).
I'll copy the content of that document in the next reply (to keep things a little less chaotic).