A lot of the big concepts are best learned through analogies because analogic thinking is how you're able to learn subsequent languages so quickly. Codeanalogies.com is an excellent resource for that. Source: over 1 year ago

For me it's free (I joined a long time ago), but their support team told me they're rolling out a paid subscription program on certain countries. Should be around $1 per month. My advice is to try Mine out to secure the free plan, or just use one of their competitors. The startup Rita (https://ritapersonaldata.com) also got funded recently and seem to get high reviews... Source: about 2 years ago