Brazilian tax lawyer or accountant: written answers on tax and compliance for a foreign company

Looking for a Brazilian tax lawyer or accountant to answer, in writing (in English), a short list of questions about Brazilian tax and compliance for a foreign company. No tax calculations needed, only whether something is required and who is responsible.

Facts: we are an EU company (Croatia) with no presence in Brazil (no branch, office, employees, bank account or CNPJ). We sell places on a 5-day professional training course for foreign dentists (no Brazilian residents) held in São Paulo in 2027 by a Brazilian host institution. The host delivers the course under its own licences and invoices us for the places with Brazilian taxes included. Participants pay us abroad. The package also includes hotel, meals and local transfers, which we book ourselves. A Brazilian coordinator helps us as an independent contractor.

Questions:
1. Must our company register in Brazil (cnpj, ibs/cbs, lc 214 art. 21 §2)? If yes, when and with what ongoing obligations?
2. Is any Brazilian tax due when a foreign participant pays us abroad? If yes, which tax and who owes it? Do hotel, meals and transfers change this?
3. Is the host-contract structure enough for the host to bear Brazilian taxes? When would a permanent establishment arise?
4. If our reading is wrong, which taxes and penalties would apply in principle, and is there a voluntary disclosure or consulta option?
5. Which visa and CRO registration do participants need, and who is liable?
6. Any advertising (cfo) and lgpd rules we must follow?
7. Does it change anything if we pay for the course materials ourselves?
8. Obligations when paying the Brazilian coordinator?
9. A short checklist before the first payment and before the course.

Deliverable: written answers to all 9 questions within 7 days. Budget about eur 80 (usd 95). Please mention your professional qualification (oab or crc) in your proposal.