I don’t think the solution you are looking for exists. At least, not to automatically translate everything from one subsite in a multisite installation to another subsite. Some translation solutions offer API access, but building the complete solution you are looking for within WordPress, probably takes more time than doing some parts manually.
I think the fastest solution is to do the following:
1. Go to the content in a Chrome browser
2. Right click the page and let Chrome translate it
3. Copy the content
4. Paste it in your WordPress installation