There is no universal template for a sales page, but there is a framework that is needed almost every time. The order of blocks follows the visitor's train of thought: first understand the offer, then believe it works, and only then decide to leave contact details.
Everything else depends on the niche. For an expensive service, a block about the team and the process matters; for a product, specifications and delivery; for an event, the agenda and speakers. It is better to repeat the call to action several times along the page rather than hide it at the very bottom.
When ads are running but enquiries are not coming in, the problem is rarely the design. The usual reasons are these.
A vague offer. A headline like quality services for your business tells the visitor nothing. They cannot see what exactly is on offer or why it beats the next tab.
A mismatch with the ad. Someone clicked on turnkey bathroom renovation in 14 days and landed on a general page about apartment repairs. They leave because they did not find what was promised, and the click has already been paid for.
A long form and slow loading. Every extra field reduces the number of leads, especially on a phone. If the page takes several seconds to load on mobile data, some visitors will not even wait for the first screen. That is why, when we build a landing page, we test its speed on real devices, not just on an office computer.
One page is enough when you have a single product or service, traffic comes from ads in Yandex Direct or VK, and the decision is made quickly. A landing page is cheaper and faster to launch and easier to test: you can compare two versions of the hero section and keep the one that brings more leads.
The format does have limits, though, and they are worth considering in advance:
A common working setup is a main company website plus separate landing pages for ad campaigns and promotions.