My question is how much cold can electronic parts survive? Because i set up a workplace outside and in winter the temperature gets -20C. So should i carry all my stuff back to house when winter comes or let them be there? Thanks for answers.
I leave my car out in the winter sometimes, they tell me cars are full of electronics these days 
Seriously, check the datasheets, often they specify both an operating temperature range and a storage temperature range. Checking a couple random datasheets, storage temperature is -65°C - 150°C.
There are three main standard temperature ranges for the operating range of components:
- Commercial grade: 0 °C to 70 °C (sometimes ?10 °C to 70 °C)
- Industrial grade: ?40 °C to 85 °C (sometimes ?25 °C to 85 °C)
- Military grade: ?55 °C to 125 °C (sometimes -65 °C to 175 °C)
Storage temperature ranges will, understandably, be outside that range. Most components you have will either be commercial or industrial grade. If the actual storage temperature is outside the operating temperature, but within the storage temperature range, then all should be well. If the storage temperature range falls outside the storage temperature range (usually below, unless you store your components in an oven) it may be necessary to "bake" the components before use.
This is most often a problem when you are reflowing surface mount components. Moisture condenses within the components at low temperatures, and when reheated to reflow temperatures creates steam which can cause the components to literally explode. It is necessary do drive off that moisture with gentle heating for a long period before use. By gentle, we are talking around 60-100°C. By a long period we are talking around 24 hours. Some components which are particularly susceptible to moisture ingress that haven't been stored in hermetically sealed packaging should be baked beforehand regardless.
Most electronic components are not damaged by 'normal' cold temperatures. -20C is not in itself a problem.
Condensation can be a problem, if the temperature cycles between warm and cold with humidity.
Batteries lose capacity in cold; so some battery powered devices might not work in the cold, but they should work again once it warms up.
Some materials will become brittle, and some things could crack from the expansion and contraction, but not electronic components (ICs, resistors, capacitors, transistors, diodes etc.).
Depending on the location, temperature and humidity, I would be more concerned with corrosion from moisture condensation and animals getting in, chewing on things and making a nest in my box of electronics.
Steve