Ok, I was wrong about "Credits" and "Support Wazapp", the exist in Transifex. Though the translated string "Support Wazapp" isn't used in the App, but "Credits" is working fine.

Regarding the other strings: "Wazapp Champions", "Thanks to", "Wiki Creator", "Icons Artist" and "Donate" definitely don't exist in Transifex, I checked the original English resource and these strings simply are not present.

Then there is another problem with the button "Open in Gallery" when viewing a contact picture. The button width exactly fits the english text but many languages have longer texts (e.g. German) so the translated string gets truncated (I'm sure this problem exists for other buttons too). One could correct this either by altering the translation (not always possible) or by increasing the button width for example. I somewhere read/heard that in UI design one should always add 20% more width/height to UI elements to fit other translations because english is in most cases shorter than many other languages.
Still the translators should optimize their translations and keep them as short as possible to avoid ugly UI glitches. (Maybe every translator should look for such problems and correct them if possible).