You are correct! Rather going here and there it is better to meet with a CA or a Tax consultant for filing crypto tax. If you cannot then there are websites like Koinly & Taxnode that can help you. They have partnered with multiple national and international exchanges. You need to connect your exchange wallet and the rest they will do it for you. A service charge will be applicable for filing tax.
I feel that giving these third parties might not be a good idea. You need to understand that they might get compromised in the future. Do remember India does not have any privacy law. As of now the government is least interested about cryptocurrency and the community that is actively using it as an earning.
It will be wise to talk to either a CA or tax consultant. If you cannot do that then use these service but insure you submit a change of wallet address request to those exchanges. As I have not used any of the recommended platforms, there is no way for me to find how they function. Do remember not to give your login credentials or your password. There is a possibility that some rogue employees from these platforms might get access to those. Be careful and never share your details to safeguard yourself.
You are also right it is wise to talk to a professional rather to an app or a website. The reason why everyone would take an app over a professional is because of the service fee. There are a lot of Indians who are using this platform for earning. They spend every thing that they earn either on themselves or their family. They might not be able to afford a repeated fee of a CA or anybody.
I know they will use a thrid part app. I do understand that the exchanges.providing such services are known by the government. I do not think that they will manipulate or scam those who desperately need an assistance.