Error creating extension PostGIS in pgAdmin on macOS

Question

I'm trying to install postGIS on my macOS.
I already had postgreSQL and pgAdmin4 installed and I just wanted to install the postGIS extension.
I used stuckbuilder to download it and followed the instructions, then I tried to create a new database on pgAdmin4 and create the extension using the following instruction:

CREATE EXTENSION postgis;

But then I got this error:

ERROR: could not load library "/Library/PostgreSQL/11/lib/postgresql/rtpostgis-2.5.so": dlopen(/Library/PostgreSQL/11/lib/postgresql/rtpostgis-2.5.so, 10): Library not loaded: @loader_path/../../lib/libssl.1.1.dylib Referenced from: /Library/PostgreSQL/11/lib/postgresql/libgdal.20.dylib Reason: image not found

What does it means and what can I do to fix it?

I already tried other solutions I found here on stackoverflow, but nothing changed. I hope you can help me.