This research aims to determine the influence of service quality on customer satisfaction at Suru-Suru All Delivery Panyabungan, Mandailing Natal Regency. The type of research is quantitative research. Data collection techniques are by observation and distributing questionnaires. This research involved a sample of 86 respondents using the Slovin formula. All tests were carried out using the SPSS version 25 program. The results of this research were that service quality had a partial effect on customer satisfaction at Suru-Suru All Delivery Panyabungan, Mandailing Natal Regency. The partial test value (t) on the service quality variable (X) was 3.769 with a value ttable is 1.663. So the tcount value is greater than ttable (3.768 > 1.663), then the service quality variable (X) has a positive and significant impact on customer satisfaction (Y). This shows that the first hypothesis (Ha) is accepted. This means that "the service quality variable has a positive and significant effect on customer satisfaction" which has also been proven successfully by this research with an R Square value obtained of 0.145 multiplied by 100% to 14.5%. while 85.5% is explained by other variables. Apart from that, the service quality variable has a low relationship with customer satisfaction at Suru-Suru All Delivery, Panyabungan District, Mandailing Natal Regency, amounting to 0.380.

This research was carried out on the basis of describing promotion analysis in the development strategy of a sustainable tofu trading business in Simangambat village, Siabu sub-district, Mandailing Natal district by taking a case study in Simangambat village, Siabu sub-district, Mandailing Natal regency, which is one of the villages whose community has a tofu trading business, namely Sustainable tofu.  This research was conducted from October 2023- July 2024. This research method uses a qualitative approach where this research describes, explains and interprets objects according to what they are. Data validation was carried out by gathering information from several informants who were directly related to the Tofu Trading Business.  Apart from that, the researcher also carried out direct observations at the research location to verify the data whether the data obtained from the informants was in line with reality data or not. As a result of this research, the author concludes that the promotion analysis in the development strategy for the sustainable tofu trading business in Simangambat village still cannot be said to be optimal. This can be seen from the marketing system of tofu factories which has not kept up with the times and is still developing a system through a system of entrusting it to stalls. So sustainable tofu businesses must develop systems such as using social media for marketing so that the business they manage can develop further and can also compete with other tofu businesses.