Yeah. That’s not a 90 stamp. That’s just immigration arrival stamp. You then have to do your 90 day report 15 days before 29 December. You can try online and if that fails off you go to stand around at an immigration office.
Other posters advising to keep money at home country are on point. Bring in what you need ideally just pension money. Make sure your home country is covered by a double taxation agreement.
Best guess is you’ll end up paying something. Your pension will not be taxable. Anything over and above that brought in may be taxable if it wasn’t taxed at origin. However - who knows.
Bottom line- if you can handle paying something tax here you may want to reconsider moving here since undoing that would be a hassle.