Spelling is an enigmatic enablling skill in PTE as you many not come to know which part of your PTE section went wrong. On the other hand, pronunciation does give you a hint that whatever you speak is not satisfying the PTE algorithm. Asians do have problems in pronouncing words accurately.
How to improve?
There are hundreds of thousands of words in English and you cannot learn all of them. But, you should focus on the words you use for PTE sections. One way to improve your spellings is writing on NotePad. Start practicing on NotePad. Once you are done with essays or summaries, you proofread your own content. After that, you cut and paste it on Microsoft Word that will show common errors in spelling and grammar. This way you learn. Grammarly and Ginger are a few more software tools that are free and help you further in indentifying the flaws in your writing.
As far as pronuciation is concerned, you can take help of Google 'speech to text' software or API. You keep the microphone on and let Google convert your speech into text. This way, you practice Read Aloud section and see whether the software is catching all words spoken.
Focus on the words that are differently written. These are the words the software could not get when you spoke. Refer OALD, Cambridge, Merriam Webster, Collins, or Longman to learn the pronunciations of the words. These dictionaries give you both AmE and BrE. Try to speak the way it is given in the dictionaries.
Speak clearly rather than loudly. Take proper nanopauses while speaking the text. This may help you ace the test.