PyQGIS: DLL load failed while importing _core. Environment path?

I would like to ask for help because I got stuck trying to code a custom application with QGIS and Python. I got some Python knowledge but I am quite new to QGIS. I tried the intro of the cookbook: Running Custom Applications.

Now while I run the code from IDLE I constantly get an error message saying:

  File "H:pathtoqgis_test.py", line 1, in <module>
    from qgis.core import *
  File "C:Program FilesQGIS 3.10appsqgispythonqgiscore__init__.py", line 25, in <module>
    from qgis._core import *
ImportError: DLL load failed while importing _core: Cannot find module..

I guess this has to do with the environment path variables, I tried alot but can’t seem to fix it. From another post out here I tried the sys.path paths, here’s mine:

C:Program FilesQGIS 3.10appsqgispython
C:UsersmynameAppDataRoamingQGISQGIS3profilesdefaultpython
C:UsersmynameAppDataRoamingQGISQGIS3profilesdefaultpythonplugins
C:Program FilesQGIS 3.10appsqgispythonplugins
C:Program FilesQGIS 3.10appsPython37
C:Program FilesQGIS 3.10appsPython37Scripts
C:Program FilesQGIS 3.10binpython37.zip
C:Program FilesQGIS 3.10appsPython37DLLs
C:Program FilesQGIS 3.10appsPython37lib
C:Program FilesQGIS 3.10bin
C:Program FilesQGIS 3.10appsPython37libsite-packages
C:Program FilesQGIS 3.10appsPython37libsite-packageswin32
C:Program FilesQGIS 3.10appsPython37libsite-packageswin32lib
C:Program FilesQGIS 3.10appsPython37libsite-packagesPythonwin
C:UsersmynameAppDataRoamingQGISQGIS3profilesdefaultpython
C:UsersmynameAppDataRoamingQGISQGIS3profilesdefaultpythonpluginsqgis2web
C:UsersmynameAppDataRoamingQGISQGIS3profilesdefaultpythonplugins

Currently I set these system variables in PYTHONPATH, and in Path:

C:Program FilesQGIS 3.10appsqgis
C:Program FilesQGIS 3.10appsqgispython
C:Program FilesQGIS 3.10bin
C:Program FilesQGIS 3.10appsqgisbin
C:Program FilesQGIS 3.10appsPython37

I’m not sure if these are correct, but this gives me the mentioned error. Now if I add:

C:Program FilesQGIS 3.10appsPython37DLLs

to the PYTHONPATH(s), and try to open my script again in IDLE, it just not opens anymore?

Does anyone see the problem and how to fix this so I can run the script correctly? I would really appreciate it. Thanks in advance!

Further notes:

• Before this I got some other errors, fixed some by installing PyQt, Python 3.8.2 (64bit) besides Python 3.7.2 (32bit) which I ran before.
• I haven’t installed OSGeo4W separately, just QGIS3.10, not sure what that OSGeo4W is exactly, I’m just trying to get the Python part to work.

set PYTHONPATH=c:OSGeo4W64appsqgis-ltrpython

python

    Python 3.7.0 (v3.7.0:1bf9cc5093, Jun 27 2018, 04:59:51) [MSC v.1914 64 bit 
(AMD64)] on win32
    Type "help", "copyright", "credits" or "license" for more information.
    >>> from qgis.core import *
    >>>