Traditionally, teaching math using English as a foreign language creates many challenges because learners may not have yet acquired the skills they need to understand the lesson. The study aimed to identify the challenges faced by teachers of math in English when course instruction shifted to online because of the COVID-19 pandemic. Also, the study presents three essential lessons from this experience from the teachers' perspectives. During the COVID-19 outbreak, all schools abruptly switched to Online Education. Most participants in the study had never done online teaching before the pandemic and were unfamiliar with using technology. The researchers used a mixed methods approach, incorporating the following two ways of gathering data: a questionnaire and face-to-face semi-structured interviews. The questionnaire consisted of two parts: (1) English language challenges and (2) access to technology. The questionnaire was administered to a sample of 50 female teachers, followed by structured interviews. The interview consisted of one question about the most important lessons learned, and the data were analysed using SPSS Statistics. The findings indicated that the English language and a lack of technology constituted obstacles for teachers. According to the participants, they identified three future lessons. The researchers provide recommendations to teachers, students, and governments.