If a SEO expert try to make 5000 back links in a month then the website disappear from GOOGLE or not???

There is no specific number, at which the site is delisted.
If the site is determined by the automated SEbot software to be using black techniques, it will be
penalised >> downgraded >> delisted.
If the generated backlinks are valid, the site will not be penalised.

Over Optimization tends to penalise the website.

Over optimization is not good to your website,it will penalised,

If you over optimize your website google will penalize it and your site will disappear from SERP.

Might be if the backlinks from same site or low quality sites.

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