Does riding a motorcycle with female colleagues and going out with them, or the presence of unveiled women, affect the validity of the fast?

The question is not entirely clear. If it is about what invalidates fasting, then a girl riding with you, or her presence in the house, or looking at her, does not invalidate the fast unless it leads to the emission of semen. However, these actions with a non-mahram (definition) woman are forbidden in Islamic law and are considered causes of temptation (fitna). You must avoid girls and adhere to your religion, not paying attention to what people might say about being strict. For whoever seeks the pleasure of Allah, Allah will suffice him against the burden of people, and whoever seeks the pleasure of people, Allah will entrust him to them. If this study leads to the loss of your religion, then you must abandon it and search for an alternative in Muslim countries.