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To my understanding you are saying that your form is loading very slowly after embedding it into your Google Website.
Please refer to https://www.jotform.com/help/19-Adding-Form-to-Google-Sites to make sure that you've used the proper instruction to embed your form onto your google site.
If this problem continues though then please let us know. Also, please additionally include a link to the page your form is embedded on within your Google Site so that we can investigate if needed.