During September 2025, Mihail Altinin focused on improving data integrity in time series analysis within the freqtrade/freqtrade repository. He addressed a bug in the merge_informative_pair helper, where the merge_ordered function previously caused data truncation and loss during time series merges. By implementing a solution that fills NaN values with corresponding entries from the informative dataframe, Mihail ensured that merged datasets retained complete and accurate information for downstream analysis and backtesting. His work leveraged Python and the Pandas library, demonstrating a strong grasp of data manipulation and analysis while enhancing the reliability of feature engineering and model evaluation processes.