You do have to very careful with disavowing links, very careful, because what a lot of business do, is upload a disavow excel document to Google, and they break links, that might be good.
so you do need an SEO expert on this for sure, they need to know which links are rubbish, which are good. I run Kingsley Fencing and a business South Wales Demolition, both had rubbish links accumulate, if left, without consulting with an expert, the organic rankings would have dropped, so do go and see an SEO agency for advice, make sure the only linking websites are quality.