Handling Missing Data in Time Series Dataset

So i am dealing with a timeseries related problem , the dataset contains solar insolation values , the frequency is half hours , each day has 26 timesteps , There are only two columns "date\_time" and "ghi ( solar insolation)" . There are around 1100 missing values (some missing values are in between two steps , some are weeks or even months long) . How do i deal with it ? Please help

data datascience dataset missing values series solar time series timeseries values