Websites like JDMFSM.com (Japanese Domestic Market Factory Service Manuals) specialize in hosting translated documents. You may need to pay a small fee ($5–$15 USD) for a high-quality, bookmarked PDF of the CN-H510WD English manual.
From the English manual:
If you absolutely cannot find an English manual, download the Japanese version from Panasonic’s Japanese support site (search: パナソニック ストラーダ CN-H510WD 取扱説明書). Then use Google Lens or the Microsoft Translator app (camera mode) to translate the pages in real-time. It’s tedious but works for critical functions like map update or resetting the unit. panasonic strada cn-h510wd english manual