How do I ensure my user knows there’s more data below this floating CTA?

I have a mobile form, on which the CTA is lower on the page, so a sticky CTA indicates the action for the form upon first glance for users. But, how do I deal with content that is hidden because of the sticky footer, below the fold?

I want to tease the user by cutting off content, to indicate that there is more content below the fold, but how can you assure this happens on every mobile device height?

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