Thanks for checking in with us, anastacio-patric.
Yes, you can record your 2017 bank transactions in QuickBooks Self-Employed (QBSE) by importing it as a CSV file. You can check out this article for the steps and details: Import transactions from other sources.
Just a heads-up, the system does not allow the filing of 2017 Schedule C. Cases like this, we need to download your Tax Summary report for 2017 and use the details on it in filling your Schedule C outside QuickBooks. I'd recommend contacting your accountant so you'll be assisted accurately in preparing your Schedule C 1040 form.
Also, you can contact Turbo Tax Support Team so you'll be guided with your Tax Filling related questions.
I have a link here where you can find articles about managing your business in QBSE: https://quickbooks.intuit.com/learn-support/en-us/banking/07?product=QuickBooks%20Self-Employed.
Fill me in if you need a hand with categorizing your downloaded bank transactions or any QBSE related. I'll be here to help.