Downtime Activity: Training
You can spend time with an instructor to learn a new language or pick up proficiency with a tool.
Resources. Receiving training in a language or tool typically takes at least ten workweeks (50 days), but this time is reduced by a number of workweeks equal to your Intelligence modifier. A negative Intelligence modifier doesn't increase the time required for training. In addition you need to find a teacher and pay 25 gp per workweek.
Resolution. At the end of your training, you learn that new language or gain that new tool proficiency.