Simple userscript for iOS/Mobile Safari
1: You will need a userscript manager on your iPhone. (Userscripts or Stay etc.)
2: Head to: https://greasyfork.org/en/scripts/560550-optitranslate
3: One installed it will automatically detect websites that are not in your native language and a will offer to translate via;
Google Translate Yandex Translate Bing Translate
4: Simple, lightweight and free