There is no crash course on IDN. Plus, anything of worthiness has long been regged. Without being absolutely fluent in a language as well as best usage (if you have a close confidant that helps - a non domainer), this is definitely not an arena to jump into.
Take every non-english language, alphabet, and dialect in the world and that is how confusing IDN can be.
Language approximate # of speakers Where is it spoken as an official language?
1. Mandarin Chinese NATIVE: 873 million
2nd: 178 million
TOTAL: 1.051 billion OFFICIAL: People's Republic of China, Republic of China, Singapore
2. Hindi NATIVE: 370 million
2nd:120 million
TOTAL: 490 million OFFICIAL: India, Fiji
3. Spanish NATIVE: 350 million
2nd: 70 million
TOTAL: 420 million OFFICIAL: Argentina, Bolivia, Chile, Colombia, Costa Rica, Cuba, Dominican Republic, Ecuador, El Salvador, Equatorial Guinea, Guatemala, Honduras, Mexico, Nicaragua, Panama, Paraguay, Peru, Spain, United States (New Mexico, Puerto Rico, Uruguay, Venezuela
4. English NATIVE: 340 million
TOTAL: 510 million OFFICIAL: Antigua and Barbuda, Australia, The Bahamas, Bangladesh, Barbados, Belize, Botswana, Brunei, Cameroon, Canada, Dominica, Ethiopia, Eritrea, Fiji, The Gambia, Ghana, Grenada, Guyana, Hong Kong (People's Republic of China), India, Ireland, Jamaica, Kenya, Kiribati, Lesotho, Liberia, Malawi, Maldives, Malta, Marshall Islands, Maritius, Micronesia, Namibia, Nauru, New Zealand, Nigeria, Pakistan, Palau, Papua New Guinea, Philippines, Rwanda, Saint Kitts and Nevs, Saint Lucia, Saint Vincent and the Grenadines, Samoa, Seychelles, Sierra Leone, Singapore, Solomon Islands, Somolia, South Africa, Sri Lanka, Swaziland, Tanzania, Tonga, Trinidad and Tobago, Tuvalu, Uganda, United Kingdom, United States, Vanuatu, Zambia, Zimbabwe.
5. Arabic NATIVE: 206 million
2nd: 24 million
TOTAL: 230 million
[World Almanac est. total 255 million] OFFICIAL: Modern Standard Arabic: Algeria, Bahrain, Chad, Comoros, Djibouti, Egypt, Eritrea, Iraq, Israel, Jordan, Kuwait, Lebanon, Libya, Morocco, Niger, Oman, Palestinian Territories, Quatar, Saudi Arabia, Somalia, Sudan, Syria, Tunisia, United Arab Emirates, Western Sahara, Yemen. | Hasaniya Arabic: Mauritania, Senegal
NATIONAL: Mali
Note: These figures combine all the varieties of Arabic. Some data sources, e.g. CIA World Fact Book, World Almanac, Ethnologue, treat these varieties as separate languages.
6. Portuguese NATIVE: 203 million
2nd: 10 million
TOTAL: 213 million OFFICIAL: Angola, Brazil, Cape Verde, East Timor, Guinea-Bissau, Macau (People's Republic of China), Mozambique, Portugal, São Tomé e PrÃncipe.
7. Bengali NATIVE: 196 million
TOTAL: 215 million OFFICIAL: Bangladesh, India (Tripura, West Bengal)
8. Russian NATIVE: 145 million
2nd: 110 million
TOTAL: 255 million OFFICIAL: Abkhazia (part of Georgia), Belarus, Kazakhstan, Kyyrgyzstan, Russia, Transnistria (part of Moldova).
9. Japanese NATIVE: 126 million
2nd: 1 million
TOTAL: 127 million OFFICIAL: Japan, Palau
10. German NATIVE: 101 million
2nd: 128 million
TOTAL: 229 million OFFICIAL: Austria, Belgium, Germany, Italy (South Tyrol), Liechtenstein, Luxembourg, Poland, Siwtzerland
11. Panjabi Western: 60 million
Eastern: 28 million
TOTAL: 88 million OFFICIAL: India (Punjab)
NATIONAL: Pakistan
12. Javanese 76 million OFFICIAL: Indonesia (esp. Java)
13. Korean 71 million OFFICIAL: North Korea, South Korea
14. Vietnamese NATIVE: 70 million
2nd: 16 million
TOTAL: 86 million OFFICIAL: Vietnam
15. Telugu NATIVE: 70 million
2nd: 5 million
TOTAL: 75 million OFFICIAL: India (Andhra Pradesh)
16. Marathi NATIVE: 68 million
2nd: 3 million
TOTAL: 71 million OFFICIAL: India (Daman and Diu, Goa, Maharashtra)
17. Tamil NATIVE: 68 million
2nd: 9 million
TOTAL: 77 million OFFICIAL: India (Tamil Nadu), Singapore, Sri Lanka
18. French NATIVE: 67 million
2nd: 63 million
TOTAL: 130 million OFFICIAL or NATIONAL: Belgium, Benin, Burkina Faso, Burundi, Cameroon, Canada, Central African Republic, Chad, Comoros, Congo-Brazzaville, Congo-Kinshasa, Côte d'Ivoire, Djibouti, Equatorial Guinea, France, French Polynesia, Gabon, Guernsey, Guinea, Haiti, India (Karikal, Pondicherry), Italy, Jersey, Lebanon, Luxembourg, Madagascar, Mali, Martinique, Mauritius, Mayotte, Monaco, New Caledonia, Niger, Rwanda, Senegal, Seychelles, Switzerland, Togo, United States (Louisiana), Vanuatu.
19. Urdu NATIVE: 61 million
2nd: 43 million
TOTAL: 104 million OFFICIAL: India (Jammu and Kashmir), Pakistan.
20. Italian 61 million OFFICIAL: Croatia (Istria Country), Italy, San Marino, Slovenia, Switzerland.
21. Turkish NATIVE: 60 million
2nd: 15 million
TOTAL: 75 million OFFICIAL: Bulgaria (Kurdzhali Province and areas of South and East Bulgaria), Cyprus, Turkish Republic of Northern Cyprus, Turkey
22. Persian 54 million OFFICIAL: Afghanistan, Iran, Tajikistan.
23. Gujarati 46 million OFFICIAL: India (Gujarat, Daman and Diu, Dadra and Nagar Haveli).
24. Polish 46 million OFFICIAL: Poland
25. Ukrainian 39 million OFFICIAL: Ukraine, Transnistria (part of Moldova).
26. Malayalam 37 million OFFICIAL: India (Kerala, Lakshadweep, Mahe).
27. Kannada NATIVE: 35 million
2nd: 9 million
TOTAL: 44 million OFFICIAL: India (Karnataka).
28. Oriya 32 million OFFICIAL: India (Orissa).
29. Burmese NATIVE: 32 million
2nd: 10 million
TOTAL: 42 million OFFICIAL: Myanmar.
30. Thai NATIVE: 20 million
2nd: 40 million
TOTAL: 60 million OFFICIAL: Thailand.
Perhaps now you and others can see why there are 6 billion people for whom English is not their native language - speaking or writting.