1. Introduction  
1.1. The revolution of extragalactic mm observations  
1.2. The nearby nuclear starburst galaxy NGC 253  
1.3. The ALCHEMI survey  
2. Observations  
2.1. Frequency setup  
2.2. Sensitivity  
2.3. Maximum recoverable scales  
3. Data calibration, equalization, and imaging  
3.1. Flux calibration accuracy  
3.2. Imaging  
3.3. Continuum subtraction  
3.4. Self-calibration  
4. ACA Data: Analysis and First Results  
4.1. Continuum emission  
4.2. Molecular emission analysis  
4.3. New extragalactic molecular detections  
5.1. Extragalactic starburst low resolution molecular template  
5.2. Vibrational emission  
5.3. Organic Molecules  
5.4. Isotopic ratios  
5.5. Opacity analysis with multi-transition CN observations  
6. Summary and conclusions