Hi,
I understand that you want tomake sure that your website is clean and safe from any any issues that can harm reputation ranking or get any penalty from Google in the future.
There can be on-site issues like:
malware on site, linking to spammy sites, keywords stuffing, incorrect use of tags and keywords, hidden text, spammy text, thin/copied/affiliate content, insufficient original content on each page or duplicate content, hidden malware, clocking (different content for users and search engines) etc....
Off Site factors:
back links from spam websites (must be removed from google by requesting), bad neighborhoood and other factors.
Please share URL and details. I will also need access to Google Console for your site. It may take 1 week or more or may be earlier.
I am available on Chat if you want to discuss project details.
About Me:
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My name is Imran and I have been working as a HTML/CSS/PHP/Wordpress Developer, Designer and Coder for the last 8 years. I have earned 317 positive reviews from my previous clients on Freelancer.com with an overall rating of 4.9/5 stars. 100% of my projects were completed on time and on 99% on budget with 27% Repeat Hire Rate. You can check all this on my profile page here:
https://www.freelancer.com/u/imranphp.html
Thank You and Good Luck for your Project.
Imran Ali.