Can anyone guarantee a first-page ranking?

The answer

No. Search results depend on many changing factors that no outsider controls, and Google states that it does not accept payment to rank a site higher in organic results. Be careful with anyone who promises a guaranteed position, a fixed timeline or a number of links. Reasonable promises describe the work, such as fixing technical issues, improving content and reporting honestly, not the outcome. Ask for examples, a clear scope and plain-language reporting.