Create SEO Website for my Company Database

Hello, I would like to create a german SEO website with different pages for each company. Our database is over 2,000 companies big and each will need its own page. We are an inquiry/hotline company in germany with our own call center. We would like to gain free traffic through good SEO placement. This is a website from the competition to give you an idea of how the website should be built: [login to view URL] as well as a page of a company: [login to view URL] The following information needs to be visible on each page: - Phone number / hotline - Email address - Website - Opening hours - Address - Industry - Company logo - General text about the company The following google keywords are important for each company: "COMPANY anrufen" "COMPANY hotline" "COMPANY Kundenservice" "COMPANY telefonnummer" "COMPANY Kontakt" COMPANY should be replaced with the company name from the database, such as Amazon, Sky, Vodafone, etc. Our website currently looks like this: [login to view URL] with the individual company pages: [login to view URL] General SEO questions: - If we are well ranked with our website - Can we change the telephone number later without being downgraded? - How long will it take to be ranked? - What are the most important keypoints to be highly ranked? - What can we do from our side to be ranked? - Can we get a guarantee that we will be well ranked? (Our own websites were never ranked) - Can we add general content afterwards without losing the rank? What questions can I answer for you? Please also describe your approach and show me your references. I would also like to have a competitor analysis to see how we can place ourselves. Best regards, Jan