Get it scanned properly and share codes. If the transmission oil has not been changed on specified duration, chances are the valve body is clogged and the solenoids are sticking. The clutches can be worn out aswell. If this turns out to be transmission failure, I know none that are capable to repair it without destroying it. New oem clutch kit was 1.3lac for 7th gen civic auto transmission 2 years back (dont ever let street side monkey mechanics touch it). You can guess it would be way more for 8th gen now (if even available). Then thorough inspection and cleanup of internals is required. Worn bearings, O rings, gaskets etc need to be procured. Then the most crucial part comes of assembly, and the common mechanics dont even know what torque wrench is. Simply put, dont go the repair route if you are unaware of the procedure, hunt junk yards for a relatively clean transmission which may work for a while (depends on how junk was the junk yard part).
