Redesigning a WordPress website to start over?

We are in the process of redesigning our website. Right now I'm at the stage where I'm starting a new website, but I'm not sure what the best way to go about it is. The goals are going to be relatively basic, no e-commerce, and not much really useful content on the site. The number of unused pages on the original site is already high, and I'm wondering if I should just get rid of all the content and start over somehow.

我有几个问题：

1.重新安装 WordPress 并丢失网站上所有未使用的旧内容有什么坏处吗？这会对我们的 SEO 产生任何影响吗？

2.我该如何在不影响旧网站的情况下构建新网站？我读过一些关于使用暂存或使用子域的文章。然后你会下载新网站的备份并将其“恢复”到现有网站以覆盖所有内容吗？

3.重新开始是否最有可能解决我们遇到的一些速度问题？