That’s just another sound. Each language only uses a subset of the full range of sounds the human mouth is capable of making. For example, Japanese doesn’t have an L sound, so people who learned Japanese as their mother tongue and then try to learn English as an adult will have trouble making the L sound. That’s not to say they are incapable of making it, but they are not used to making that sound with the speed and ease needed to use it as a normal part of speech. This can be learned with practice, but it takes time.