First, mark the camshaft and crankshaft gears. Then, place the piston of cylinder one on its compression stroke. Move the camshaft so that the valves of cylinder four are overlapping. After this procedure, release the tensioner, remove the belt, and replace as many parts as possible: water pump, water seals, belt, and tensioner. Make sure the gears don't shift even a tooth, otherwise, the engine will be too big. If you have it done at a shop, it will cost you around 40,000 or 60,000 (currency unspecified) depending on the shop, but if you do it yourself, you'll save a lot of money. I hope this helps
. Goodbye.