I have a dream of becoming a long term bitcoin holder but, dreams aren't achieved with words alone,
If I am advising anyone to invest in bitcoin, then I will recommend they invest for the long term. I notice you are a newbie, and trying to trade or invest for short term might be very risky, because you can easily lose your money due to the high volatility in the market currently. If you buy and hold, then your chances of losing your money is kind of low, but there are still some necessary things that you have to do to secure your bitcoin if you are planning to hold.
Make sure you don’t leave your bitcoin on exchange. I can say that’s one of the main mistakes that newbies make, they believe that if they leave their bitcoin on exchange, it can be easily accessed, but they don’t know that if anything happens to the exchange, then their investment is already gone. Make sure your bitcoin is stored in a non-custodial wallet address where you are in control of your coin, and make sure you properly secure your wallet private key. If you lose your private key, then you are losing your bitcoin. That’s why your private key should be properly secured. You will need to take your time to read about wallet security, because when holding you need to protect your wallet.
an action is needed for the start up, so I have decided to sell one of my less used phone for the purpose of buying bitcoin.
I know you are so desperate to invest in bitcoin, but I don’t think it’s a good idea for you to sell your phone to invest in bitcoin. What happens when you need the phone later in the future? Are you going to sell the bitcoin to buy back the phone? Bitcoin investment should be done with the extra cash that you have with you, you don’t have to hurt yourself because you want to invest in bitcoin or sell your properties because you want to invest in bitcoin.