Unfortunately the negative Y-axis gone (the position of graph changed) and the pourcentage in the right is showing -20000000%

how can I get back the Y-axis, and how can I declare the 100% be the value 300000000 ( so the graph will show 20%…40% and the value 300000000 will represent 100%

It appears Transform is disabled because you are still using the traditional alerts.

Can you calculate the percentage in a second Influx query? Then assign those series to the second y axis, set axis unit format to percentage (to get the % label).

SELECT cumulative_sum("change") FROM (
SELECT difference("metric")/first("metric")*100.0 as "change" FROM "results" WHERE $timeFilter fill(previous)
)

The above is just a random example, but if creating Influx queries is not your strong point, you could also try posting the question on the InfluxDB forum.