BERT Stands for Bidirectional Encoder Representations from Transformers. It is Google’s neural network-based technique for natural language processing (NLP) pre-training. For more information, you can read this blog from searchengineland, I am sharing the link with you.

https://searchengineland.com/welcome-bert-google-artificial-intelligence-for-understanding-search-queries-323976

You can target the audience on facebook by optimizing it properly. Follow the tips to target the audience.

1. Compile data on your current customers.
2. Look to the website and social media analytics.
3. Check out the competition.
4. Create a target market statement.
5. Test social ads on your target market.

@seoradar

Yes

There are many tools which can help you some are paid and some are free. Paid are - Aherf, Semrush, Keywordeverywhere.

If you are looking for a free tool then you can go for Ubbersuggest.

Yes, the Link building will be relevant in 2020. It will play a big role in the digital promotion of any business. Link Building built credibility, and help your brand rank higher on search engines. That's why it is vital to make link building a part of your SEO plan in 2020.