For small memory makes HTC500 unfortunately almost useless!

I have the HTC 500 arrived for 3 months in use and am now on the border of the far too small internal memory. Indicated this memory with 4GB, which are however already 3GB Internally connected to the system and all the pre-Google programs. The free 1GB are occupied quickly; next WhatsApp, weather and a safety program I plan only 6 other apps (not games!), and now is no room for new apps, even for upgrades and updates!
Of course, I tried to push the Apps largely on my 32GB memory card, but despite the setting "Primary storage always to SD card" can be many apps not unfortunately move! Other preinstalled apps, such as Facebook, can not be deleted and only take unnecessary space. What shoud that? Despite regular emptying of the app caches I am so quickly reached the limit of memory capacity, it unfortunately does not make sense to continue using this otherwise very good phone.
If anyone knows any advice, what else could possibly try - let me know! Downloading a cleaning tool but unfortunately did not work out: "Error - There is not enough space on the device available" :-(