I have a 1998 Honda Accord 4 cyl. It takes 25-30 minutes to heat up. If I don`t let it sit then it has trouble shifting out of 1st gear and wuill make a hard thump. But when it does heat up it`s perfect. Can you please help.

It's time for you to change the transmission fluid. Using a full synthetic fluid, such a Mobil 1 Synthetic Multi-Vehicle ATF, will help it shift properly without needing to be warmed up:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-12.html#post2295563

Easy job.

With the engine at normal operating temperature, remove the dip stick, remove the 3/8-inch transmission drain plug with a ratchet wrench, drain all of the fluid into a suitable container for recycling, replace drain plug, refill with approximately 3 quarts of ATF, and replace dip stick. Afterwards, start the engine and move the gear selector through each gear, pausing several seconds in each. Check the final fluid level, when the engine is hot, level, and in Park. Change ATF every 30,000 miles or 3 years, whichever comes first.

Is that 25-30 minutes for the ATF to get warm enough that it shifts good or does your engine actually take that long to warm up? Whereabouts do you live (state or province)?