Congratulations on your first job! It's great that you won't let stuttering hinder you. I also have trouble speaking clearly at times, especially when I'm talking fast due to nervousness or trying to get past a word quickly. My parents and friends often ask me to repeat myself, with the most frequent advice being to take my time and enunciate. Sadly, I haven't completely fixed this issue, but I'm not sure this is a fixable issue (kind of). It takes practice to speak clearly, and reading an article passage every once in a while has helped me focus on fluency and verbal efficiency. There will certainly be some days where you trip up, perhaps have a hard time speaking clearly. But as you continue speaking, those days will be fewer and farther in between. It can also be beneficial to choose certain words that give you a harder time than others and sounding out those syllables before moving on to stringing longer phrases together. Another key thing I learned was to remain calm and take a deep breath before saying anything. Any anxiety will often trip you up.