select substring(t.link, position('variable2=' in t.link)+10, position('&' in substring(t.link, position('variable2=' in t.link)+10))-1)
from (select 'https://website.com/?variable1=aaa&variable2=222&variable3=ccc&variable4=dd44' as link) t;

substring(string from pattern for escape)

substring(t.link from '%variable2=#"%#"&%' for '#'),
substring(t.link from 'variable2=(.+)&')