Gear problems Suzuki Jimny

Hello I have a Suzuki Jimny BJ 2001. I have the following problem: the first gear can be badly inserted in a warm state, if you are standing at a traffic light and want to switch from idle to first gear it can be that you press against a lock. Often it works with some resistance the second or third time. Can really annoy in city traffic at Stop and Go. Without any problems the first gear goes in when you switch directly from reverse to first. Otherwise go all gears in without any problems. Kilometers I only have 26000 on the speedometer.The dealer has filled an additional medium in the gearbox at the beginning I thought it was better, but at the moment he is not going quite clean the other time again. According to the announcement of the dealer the gears are generally a bit tacky!! Can someone give me a tip what I can do? Greeting gladly-schlaeft