Yr 1st transmission sycronizor is going slowly, prevoius user has mis-used his ex- car.
2 options,, rebuild transmission,, this i personally wont recomend.
2nd option,, swap transmission. (gearbox) sell old one and buy another,,
i have a 3 months used jdm transmission for sale from 4afe corolla,, asking price what ever is going rate .. garanteed all functions work fine. tested for 3 months in car.