Power Bi data evaluation (questions are described below)

1st question: I have 2 columns that I want to add together (Power A + Power B), I would like to display these in the line chart, unfortunately with Power BI I can only set: Maximum, Min, Count, Sum, Median, Variance etc, but I want to have the real value (only Power A + Power B).

2nd question: Sometimes Power BI does not recognize the decimal point and displays e.g. 5.6 kW + 10.5 kW as 16.1 kW, which would be wrong (see picture). How can I prevent this? I have already tried to correct the decimal places using column tools (data type and format), but without success.

3rd question: I want to load some values from an external excel table into the current table, but haven't found a way to do this yet. The values in the excel table have a timestamp (date + time in h), in the table the time is in minutes. How do I import the data and add the values to the correct date? I will show more pictures and files in the next days. I hope you can help me. Question: How to change minus values in the table to plus values? I have in the table various measured values that are given in minus, which actually do not make sense since they are producers. Question 4: How to change minus values in the table to plus values? I have in the table different measured values, which are indicated in minus, which actually do not make sense since they are producers. 5th question: I have additionally an Excel file I should add to this diagram. Problem here: Partly the date is not present in one or the other file. I just want to add them on a separate column, but they should match the date of the other values. What is the best way to solve this? Thanks a lot for your help! With kind regards Nik Nak