Ge ahold of an very good real estate attorney right away. You could end up on the very short end of the stick!

Not sure what you mean by HOA fee vs assessment. Are you refering to regular assessments vs special assessments? 
 
Assuming that being the case both must be disclosed, but ..... Special assessment is recorded at the time it's imposed. So technically you are not responsible for it - the original owners is.

To add to Jeff's remarks. . . 
 
 
 
HOA assessments cannot be negotiated. The buyer will be obligated to pay whatever the current assessment is and it runs for as long as he is a member of the assn. A special assessment may only run for several months or a year but here again the amount cannot be negotiated.

This may vary by state, but in California a full amount of special assessment is recorded at the time it's happening. Owners maybe given an option to pay it over time with no penalties. Lets say a spesial assessment is passed for $1000 per unit. Owners are given an option to pay $100 per month for 10 months starting in March. 
 
An owners sells a unit a June having only paid for four months or $400. The remaining $600 must be negotiated between the buyer and the seller. If that was never disclosed and buyer moves in, the association can't go after the new owner for this money. They must go after the original owner.  
 
This is because the entire $1000 assessment was recorded back in February when the original owner still owned the unit.

The buyer's attorney must ask the owner's association for a statement of unpaid assessments at the time of closing. Don't rely on the current owner to disclose it properly. In my state (sorry, not Ohio) the new owner is not liable to pay assessments in excess of the association's statement, so the association better know what it is doing and disclose any / all unpaid assessments, even if an unpaid balance is in a payment plan.  
 
Both the new owner and the previous owner are jointly and severally liable to pay the association any unpaid assessments (in my state), so yes, the new owner must continue to pay. However, if a new owner pays the assessment of a previous owner, then the new owner may recover this from the previous owner, since unpaid assessments are an unpaid obligation of the previous owner. IMO, it does not matter if the unpaid amounts were disclosed or not: the previous owner is liable for unpaid assessments. (Check the law in Ohio.) 
 
So it is important to determine what are the unpaid assessments, if any. Jeff Ross is correct that a Special Assessment is recorded at the time it's imposed. So any balance due on a special assessment is unpaid assessment. There may be a payment plan with a term, but the full amount of the special assessment has already been assessed to the previous owner, and any balance remaining on a special assessment is unpaid. At least, that is how it works in my association.  
 
What is the nature of the payment and term in your question?  
 
 

I have a condo in San Diego CA.that are just only 8 Units.6 of them are rented out. The Landscape is in total abandoned and neglected,the stairs are falling apart. The HOA do not nothing to fix them , Where can I complaing about this bad situation?..

you can complain to your board of directors. if you are not happy with their performance you can elect new members to the board. You are one of the owners and you can only complain to yourself for allowing this to happen

We have recently received notice of a "special assessment" to repair garage roofs. Ct. documents indicate that special assessment money should be put in a separate account to be used for that purpose 
 
only,Our associatio is adding the amount to our common charges. Isn't that illegal? Incidentally we have a reserve of over $305,000. We have 136 units. I feel we are being il-advised.

This happened to me too. Seller added her special monthly assessment payment (to continue for the next 11 years) to her mo. maintenance fee (which covered landscaping, mowing, snow removal, exterior bldg., reserve fund) and did not disclose that there was an assessment in that total that she agreed to pay. I could not negotiate it. Title company dropped the ball and failed to get that info. from assoc. (not liable as it was a non-recorded assessment); realtor never verified (sloppy but not illegal) that maintenance fee on his MLS form. My purchase contract prepared by realtor said NONE for any assessments due. I sued seller and title company to pay the remaining $$ assessment and lost. That was "disclosed" by her adding it to her maintenance fee and I assumed that that was the HOA I as bueyr have to pay. I never agreed to any assessment!!!! THEN after title closed, the association secretary destroyed the paperwork which seller originally signed agreeing to pay the assessment over 15 years. All LEGAL! I found out seller concealed the assessment payment in the HOA fee AFTER closing. BEWARE in OHIO. SELLER does not have to disclose an assessment. YOU HAVE TO FIND IT.