The answer to 'how to fix bathtub' is to first identify the specific issue, such as a clogged drain, leaky faucet, or damaged tub surface. For a clogged drain, you can try using a plunger or drain snake to clear the blockage. For a leaky faucet, you may need to replace the washers or cartridge. For a damaged tub surface, you may need to refinish or replace the tub. Be sure to turn off the water supply before attempting any repairs and wear safety gear like gloves and eye protection.
If the issue is beyond your DIY skills or comfort level, it's best to call a professional plumber to properly diagnose and fix the problem. Plumbers have the tools and expertise to safely and effectively repair bathtubs and prevent further damage.