My dashboard is showing F signs

Hate to be the bearer of bad news but the F sign usually means a very expensive repair . You need to scan the transmission ECU for fault codes with a suitable scanner capable of doing so , such as tech 2/3 or opcom.

I had the same fault.
It turned out to be the alternator not giving out enough Voltage.
Replaced alternater Fault cleared ok.

Glad you got it fixed , never heard of that before on an automatic as the flashing F means its gearbox related and .anything else like a faulty alternator and you usually will have the engine management light , battery light or spanner light on.