Is my forecast value right

Hello Everyone

So i want to ask i use power bi desktop line visual to do forecasting the result i get 

that's only one site data i'm sharing i do forecast for 819 site some of them giving me this issue not all 

Month         Total             forecastValue
1/1/2017      40000
2/1/2017      32000
3/1/2017      40000
4/1/2017      40000
5/1/2017      40000
6/1/2017      40000
7/1/2017      56000
8/1/2017      48000
9/1/2017      48000
10/1/2017    48000
11/1/2017    32000
12/1/2017    64000
1/1/2018      48000
2/1/2018      48000
3/1/2018      40000
4/1/2018      56000
5/1/2018      56000
6/1/2018      32000
7/1/2018      48000
8/1/2018      48000
9/1/2018      56000
10/1/2018    48000
11/1/2018    40000
12/1/2018    32000
1/1/2019      32000
2/1/2019      24000
3/1/2019      0
4/1/2019     8000
5/1/2019    15791.2
6/1/2019    8000
7/1/2019    0
8/1/2019    0
9/1/2019    0
10/1/2019    0
11/1/2019    0
12/1/2019    0
1/1/2020                      -4171.365423
2/1/2020                      -7081.240127
3/1/2020                      -14758.11214
4/1/2020                       690.922017
5/1/2020                       6299.942931
6/1/2020                     -10170.33298
7/1/2020                     -1859.007765
8/1/2020                     -2250.080454
9/1/2020                        2120.82186
10/1/2020                    725.6093023
11/1/2020                   -6635.075564
12/1/2020                    2119.905997

So first of all i'm getting negivate value not sure if that's right i use build in forecast function

2nd when i show this forecast value to my boss he said the value is wrong as well value should not be negivate

3rd is this because of 0 value i have against some months

can anyone share some thoughts on this

thank you