I have some experience in windsurf and surf from my young age where I used to practice every summer those kind of sports fsince 18'. Now I am 31. Usually I work as lifeguard in summer and in the sparetime I tried many times to surf on rescueboards, I went out sea in every condition possible with those damn things, long and narrow, and of course it is veeery hard to stand on them. Sometimes I could catch a good wave, but countless times the top just go into the water and make me fall, no matter how far I sit from the tip

Now I've decided to buy for me a real surfboard. I found a 6'5'' long, 1'15'' width and 18'' thick board. I am 5'7'' tall and 154 libb, good swimmer, well trained.
The board I've found has a narrow tip, is like a gunboard (I think? not very expert in specific terms this is why I need help

1-it is cheap and as a "beginner" I dont want to spend 500 on a board I will probably smash and use intensively
2-it can fit in my very small car
3-I live 40min to the sea and buyng a board will push me into doing surf every time possible.
Heres the link to the board --> https://www.subito.it/sport/surf-massa-carrara-384650464.htm <--
Another thing that concern me is that the fins seems permanently attached to the board and the owner told me it has 10+ years, he used it like 2 times.
Yes, yes, I have read many and many advices to beginners to start on with a long/fun/minimalibu, at least 7-8' long but I just need to hear some advices about my specific situation from more experienced ones, just to be sure.
Thanks to the ones that will kindly help me!